Tanks don't start out as some narcissistic jackass with an ego larger than Pauly Shores, they become that.
I was once a guy who hated those tanks, but after gearing TWO characters, JUST 2, I lost all faith in humanity.
If you really honestly have no idea why tanks hate it, reroll one. I'll paint you a picture of my day before I quit WoW:
You log in, check mail, and then queue up-oh snap it's already popped after 2 seconds.
You're in a group with 1-2 retarded dps, and 1 insanely good one with an equally large ego, and a healer who would rather be fapping to hentai. You're buffing (if you have buffs) and are waiting for everyone to buff, and one of the dps is just saying 'go go go go' as if they speak Portuguese and are unaware of any other English words.
You are pulling at a brisk manner, usually downing the wing in the time of 1 ae cd (~8 seconds) and are moving fast but are constantly being berated by that same moron.
You also pull up recount being insanely bored, and notice that you're heads and toes above the entire group in damage. And not even a paladin (sometimes)! You get to the first boss, and if it requires any sort of non tank-and-spank strategy, you're going to lose someone, as they usually will stand in fire or do something stupid. So, you either lose the moron dps who will initiate a vote-kick to kick the healer for not healing them with the throughput of a raid-tank healer WHILE healing the actual tank, or the good player dies, and initiates the kick for the moron who fucked up!
All the drama goes on for a few minutes, minutes you could be clearing, and the third dps chimes up that we should just continue the dungeon, or he just /leaves with better things to do. The healer then becomes frustrated with the moron dps and leaves, and the other 2 dps find that replacing a healer is just too time consuming, and opt to leave.
You are almost immediately given a new group and/or dungeon to start the process all over again.
I found after 1 day, that taking a break between bad groups helped somewhat, but not a lot. People are just morons, and tanks are either the moron of whom they perpetrate and persecute, or are the intelligent ones driven mad by the astounding amount of idiocy. I am probably the former, but yeah, you get the picture.