Auto attacks are important because skills have cooldowns.
If your last skill got really, really, really close to defeating an enemy, but they survived with a tiny sliver of HP, auto attacks can finish them off before your skill comes back.
It’s the same reason all casters have a spamable zero cooldown spell. So you’re never stuck waiting around for a mostly dead enemy to get all the way dead.
Wish my casters would swing daggers, swords and maces… or shoot wands as auto-attack.
Auto attack exists so we can pummel critters.
Auto attack exists to make sure melee specs don’t look stupid at different APM’s. If you were to remove auto attack, an Assassination Rogues would often end up just staring at their target for a couple of seconds before going back to attacking. Reducing the energy cost of their abilities to allow them to attack every GCD would drastically alter their gameplay. And this holds true for many melee specs.
I don’t think I even auto attack anymore, I use tab targeting and vision targeting so I’m just blasting without clicking on anything
Make autoattack do big damage. Then you can play the game with people who aren’t good at it, and still complete content.
Continuing to autoattack allows you to kill mobs if your network disconnects, so you don’t stand there and die like a dope.
That tiny thing alone is worth more than any reason to remove it.
So you arrogantly think you know how to code the game better than the devs? This is what I infer from your post.
Exactly
I think they tried experimenting with removing auto attacks with monks when they first came out. The choppy gameplay wasn’t recieved so well.
A bakers dozen?
Gen Z trying to cancel auto attack 
Auto-attacks are pretty important for…
Rogues (Poison application and Assassination’s entire kit revolves around auto attacks, Outlaw mastery, Subtelty combo point generation)
Hunters (Roughly 30% BM’s damage is auto attacks by the hunter and the pets. Lock and Load and Deathblow procs for MM)
Druids (Feral’s Omen of Clarity, Guardian’s Tooth and Claw)
Death Knights (All three have a lot of auto-attack-based procs)
Enhancement Shaman (Pretty much all of it)
Warrior (All three specs, not just Arms/Fury)
While I don’t play Demon Hunter or Paladin, both Ret and Havoc end up replacing their basic no-CD builder to something that procs off of their auto attacks so GCDs aren’t tied up in filler. I also don’t play monk and haven’t even looked at it since the rework so I won’t comment there because that would be outdated information though they probably have procs somewhere.
Pretty much every non-caster spec relies on auto attacks for something.
Oh neat, so they slapped that concept into Plunderstorm instead.
Because it is still a virtual world and can’t remove all realism
OK.
(Disclaimer: For most of these i looked at the talent trees. I may have missed some, especially if they are part of the class/spec but not in a tree. I started alphabetically with Death Knight and stopped after 20 talents.)
Death Knight - 8*
1: Runic Attenuation - autos have a chance to generate runic power.
2: Permafrost - Autos grant an absorb shield equal to 40% of the damage.
3: Insidious Chill - Autos reduce the target’s auto-attacks speed by 5%, stacking up to 4 times.
4: Bloodworms - Autos have a chance to summon a bloodworm. Worms deal damage to mobs and burst to heal the BDK.
5: Sudden Doom - Autos have a chance to make your next death coil cost less runic power, crit, and burst a festering wound.
6: Killing Maching - Auto crits have a chance to make your next obliterate crit.
7: Icy Death Torrent - Auto crits have a chance to send out a line of frost damage to enemies in front of you, providing aoe.
8: The Long Winter - Auto crits increase pillar of frost duration by 2 seconds, up to 6s.
Smothering Offense is technically an auto-attack talent, but it’s purely increased auto damage with no extra effect so I’m just mentioning it without counting it.
DH - 4*
9: Demon Blades - adds shadow damage to autos and makes them generate fury.
10: Live by the Glaive - when you parry or are parried (autos mean more parries if you are in a position to be parried) you heal and generate fury.
11: Wounded Quarry - melee attacks against your Reaver’s Mark target do more phys damage and can shatter a soul (extremely vital for aldrachi).
12: Burning Blades - Chaos Strike, throw glaive, and auto attacks apply a dot for 35% of their damage as fire. While it’s pretty much just more damage, it’s damage that keeps working for 6 seconds after leaving melee.
While Any Means Necessary does interact with both demon blades and burning blades, it just converts them to chaos and makes them do more damage so i wont count it.
Druid - 3
13: Omen of Clarity - Autos can make your next shred, thrash, or brutal slash / swipe cost no energy.
14: Tooth and Claw - Autos can make your next cast of maul/raze deal more damage, cost no rage, and reduce the target’s damage to you for 6 seconds.
15: Ravage - Autos can turn your next Ferocious Bite / Maul into Ravage (this is the Druid of the Claw core talent and so has things that build off it).
Hunter - 5
16: Lunge - Autos reduce the cooldown of wildfire bombs by 1s.
17: Lock and Load - Autos have a chance to cause your next aimed shot to cost no focus and be instant.
18: Wild Call - Auto crits have a chance to reset the CD of barbed shot.
19: Snakeskin Quiver - Autos have a chance to also fire a free cobra shot.
20: Bleak Arrows - Autos now deal shadow damage and have a chance to grant Deathblow, which is basically warrior’s “Sudden Death” but for Kill Shot.
Now to be fair, most of these do fall into the categories of “generates more resource” or “procs something” but it’s a lot more than just a couple small things for a couple specs like you seem to think. Keep in mind that i stopped at 20. I didn’t even look at monk, paladin, rogue, shaman, or warrior, and as others have mentioned some of those specs go a bit crazy with the auto attack interactions. Could they change ALL of these talents and interactions to be off different abilities and/or baked into the classes and tune accordingly? Maybe, but why? What problem is being solved here? Do you want more button bloat and rotational complexity, or do you want the passive effects that are happening to just happen from the things we are already pressing?
HEY. Don’t blame me for this inept thread!
How dare you. One of life’s tiny joys is watching my fire kitty pointlessly swat the Lich King while waiting for the monologue to end.
I just use lpt for extra fast looting lol
But it’s not pointless. 
I’d settle for right-click to auto loot that actually loots and doesn’t just leave stuff on the corpse and/or force you to manually click each piece of loot like it’s Classic all over again.
Heck, I almost walked out of a delve without the disc fragments earlier today because I opened the chest and for some stupid reason, my character didn’t grab the disc fragments and I didn’t notice until I was like 3 feet from stepping through the fog door and I had to go all the way back to the treasure room, only to see an open chest (which means I DID open it!) with the disc fragments inside that the game didn’t loot for whatever reason.