People on your team banning your pre select pick

Vanguard main here, I was basically a hulk one trick for a while but I learned other vanguards like strange and groot because of his high ban rate. Still my hours, mechanics and just general skill on hulk is definitely way higher than any other character. Now I’ve had this issue a couple times over the last couple of days multiple times where I pre select hulk, and my own team bans my pick!!! It’s so infuriating because I’m trying to pick my best tank ( a role nobody wants to play already) to give us our best chance to win and my own team actively works against me.

I of course still try to win but it just feels like friendly fire and when I’m a couple wins from GM it’s super annoying. I guess my only question is for people who do this, why? I hate playing against cloak ult but if my teammate pre selects her you best believe I’m banning someone else.