The main 5 reasons I stopped wanting to tank and now only do it when I need Mythos:
1) DPS and healers are too rude to tanks too often. I get b*tched at if
-a) a mobs slip past me even if not at fault (attacking wrong targets or putting regen before flash/overpower)
-b) I take too long marking targets
-c) I don't mark targets
-d) I don't pull enough mobs
-e) I pull too many mobs
-f) I die regardless of fault
-g) I make any playstyle suggestion to others
^This list can go past Z but these are the most common to me
2) Too much is expected of me. I am expected to
-a) grab mobs if a DPS/healer pulls ahead of me
-b) stop every interruptible attack without fail
-c) avoid all AoE while not moving mobs for melee (the point here is you can't do both normally)
-d) position myself so that no one gets hit by any cone AoE*
-e) play and adapt according to others' playstyle
3) I get type casted automatically as being hostile just because I'm on a tank class. Others always just assume I'm angry even for politely asking someone to follow marked targets, asking anyone to do something a different way, or explaining what caused a wipe. I get told to "calm down" or asked "u mad?" so often on tank compared to when I say the exact same things on DPS or healer. (though I will concede the reaction to explaining a wipe is similar when on DPS)
4) I can't play how I want to. How many mobs I pull is up to the healer and determining how I get hate is up to DPS (AoE vs single target or just both at the same time). I like having structured runs that go smoothly rather than "do as you please" runs but it's so frustrating when people go against the grain for whatever reason that now I just yolo every pull not caring and just grab hate back if I lose it for whatever reason.
5) The only thing I don't get blamed for on tank is when something doesn't die fast enough.
*The reason I mention positioning is because people often get swiped at their own fault by stuff and blame tank for not positioning right. tanks are always expected to be mindful and adjust themselves according to wherever people want to move