You are correct, but what you’re missing is that the original game design also led to unforeseen consequences. And those unforeseen consequences are what caused Blizzard to add dual-spec.
Keep in mind, WoW was one of the first RPG’s to allow people to respec, even though being able to completely change your character makes no sense in a roleplaying game.
I think Blizzard conceived of WoW as a true RPG. The only reason they offered the ability to respec was because of the sheer time investment in your character. In Diablo 2 if you messed up your talents you could just throw your character away and re-level another in a day. Blizzard understood people might have leveling specs, or they might just mess up their spec, but Blizzard ultimately wanted to effectively lock people into their specs to keep true to the RPG experience.
When the 50g respec was decided upon, the game hadn’t yet launched, MC didn’t even exist, no one knew anything about the game, you didn’t get gold from doing quests at max level, there really was no “end-game” as we imagine it, and there weren’t yet bots.
If you adjusted that original 50g cost to Classic inflation today, it would be somewhere around 250-500g.
When WoW first released there was no honor system, no battlegrounds. They added the Honor System something like six months later, and PvP remained largely unimportant and uncompetitive in Vanilla WoW. Plus the non-raid content was so easy you could do it with practically any group. In fact, for around the first year of WoW the level 60 dungeons were all 10-mans, and UBRS was a 15-man. I can remember people doing “class runs” through Strat and Scholo because everyone wanted that Dungeon 1 set.
While people may have wanted to respec at times in Vanilla WoW, there really was no pressure on anyone to be a min-maxing tryhard. But in TBC, PvP became increasingly the center of the game. At first the vast majority of the playerbase treated PvP much like they did Vanilla PvP. No one really had much resilience, no one was pushing too hard to rank. Arenas were just a fun extra that only a few PvP lovers really got into. But by late-TBC, PvP was basically the entire game for many people, raiding was just something to do on the side with your guild/friends.
In vanilla, prestige came from being in a guild which could clear the raids. In TBC, prestige came from having the gladiator title, or being one of the top teams on your realm. And because arena specs usually performed poorly in raids, this forced people to make a decision, either cough up the gold to respec every time you want to raid or pvp, or raid and/or PvP in a subpar spec.
Now, you could get away with a subpar spec in Vanilla and maybe some early TBC raids(especially after they were nerfed in patch 2.1). But Sunwell was very tightly tuned. If you didn’t show up to the raid in an optimal spec, you couldn’t kill the bosses.
The effect of the 50g respec was to basically split the TBC community in half. With some pretty much only raiding, and others pretty much only doing PvP, regardless of whether they wanted to do both.
After four years Blizzard finally realized that locking people into their specs is a stupid idea that only limits what players can do, and in many cases prevents them from playing the game. In vanilla, where PvP was mostly a time investment, this limit didn’t create the kind of backlash that came in late-TBC, when PvP became the most important aspect of the game, and where tanks were absolutely useless in PvP.
The original implementation of the dual-spec was aimed mostly at allowing people to raid and PvP without having to pay 100g. Healers also wanted dual-spec to make it easier for them to farm for raids. And others wanted dual-spec as a solution to the tank/healer shortage. But dual-spec is actually pretty limiting. It is not a free respec and most people chose a PvP spec as their second spec, so it didn’t necessarily address the healer/tank shortage in a meaningful way.
As I said, I’m not an advocate of dual-spec, but I hate the 50g respec. It is absolute trash. It is a literal cancer on the game and is killing it, and it serves no actual beneficial function. I have no idea why anyone defends it, other than their mistaken belief that it is some kind of amazing gold-sink.