Need burst? Shoot them in the head with Widowmaker.
Need flank distractions? Bait people with Tracer and Sombra.
Need CC? Stop 'em in their tracks with Sombra, McCree, Doomfist, and Junkrat.
DPS exist because some people want to actually challenge themselves when playing a game.
Sure. We could all just run Brigitte, Reinhardt, Sym, Mercy, Winston and Junkrat.
But that’s literally the most boring possible thing. At least to me, and most of the people I play with.
Some people get a thrill off that amazing headshot on the half-health Nanoboosted Soldier with sights up shredding the backline and dps.
Some people get a high when they land that perfect hook on the D.Va bomb into a pit, knowing that it was insane.
Some people just love to come in when we’re down 3 people, and Dragonblade the numbers down to 3v3 and then pick someone else off, knowing they just turned the fight for the better.
Some people like to hold m1 and run at others. Yee.
The point is two pronged, and A) DPS can do anything damage related far better than most supports and tanks usually can in most circumstances, unless tanks and supports are given opportunities for false economy (situations where they’re able to outplay due to sheer skill gap or ignorance of the victimized player), or the enemy team merely lets them. And as for B) and by no virtue of the player being at fault, most supports are just innately boring by design. You can just thank Blizzard for that.