It is simple enough.
The tank has the least glamorous job. They simply stand around and get punched in the face. You are a meat shield, and you will note people rarely speak kindly of shields except with the shield is a metaphor. In doing so, your items will get trashed (getting punched in the face by enemies swinging limbs the size of a city bus is bad for your armor it would seem), meaning in any given battle you will earn less money than, say, a mage who (ideally) never got hit at all. Yet, in spite of the fact that there is little glory to be had absorbing damage for the good of the group, it is the single most important aspect as the tank enables each and every other class to be successful at their job. The tank, then, lets everyone else focus on doing one thing really well.
But, there is no glory to be had in being the tank. If the DPS pulls aggro at an inopportune moment (between cooldowns for example), there is little you can do to yank it back. The DPS gets into a mess and they expect the tank to get them right back out. And, much of the time, the tank does exactly that. But on the rare occasion that they do not, the tank is blamed for failing at their job. A rather unfair accusation in my book as the tanks job of holding aggro is only going to be successful so long as the squishier members of the group do their jobs such that they don't cross the aggro threshold with damage or healing. Thus, a tank is culpable not only for their own legitimate mistakes but also for the mistakes of others in the party.
Really, it is much the same problem that healers face. In both cases, your job is that of enabler. You keep the tanks standing and absorbing punishment. You pick up the slack when things go pear shaped and hopefully mitigate the damage while the tanks get things under control. In either case you can do your job perfectly and the raid can still fail and you will be blamed.
The reason no one wants to play a tank (relatively speaking) and no one wants to play a healer are related. The problem is that DPS players are, on the whole, the worst sort of person in the game. Where the tank and the healer emphasize the cooperative nature of the current endeavor, the DPS game is intensely personal. People want to put up the biggest damage numbers and they simply expect everyone else to bail them out when things go wrong. It is these players who will cry the loudest when the party wipes even if the very action that caused the cascade failure was their own (They pulled aggro at an inopportune moment for the tank, the tank desperately tries to get it back, the healer tries keeping the far squishier DPS member alive which results in the tank collapsing under the (probably still) high level of sustained DPS leading quickly to a party wipe).
Of course, there are plenty of DPS players that are not utter dicks blind to the fact that they are as responsible for their own survival as anyone else in the group but thanks to the fact that any PUG is going to feature a number of such dicks ensures a tank will quickly tire of their nonsense and either stop playing or find a guild to act as a filter.
The tank has the least glamorous job. They simply stand around and get punched in the face. You are a meat shield, and you will note people rarely speak kindly of shields except with the shield is a metaphor. In doing so, your items will get trashed (getting punched in the face by enemies swinging limbs the size of a city bus is bad for your armor it would seem), meaning in any given battle you will earn less money than, say, a mage who (ideally) never got hit at all. Yet, in spite of the fact that there is little glory to be had absorbing damage for the good of the group, it is the single most important aspect as the tank enables each and every other class to be successful at their job. The tank, then, lets everyone else focus on doing one thing really well.
But, there is no glory to be had in being the tank. If the DPS pulls aggro at an inopportune moment (between cooldowns for example), there is little you can do to yank it back. The DPS gets into a mess and they expect the tank to get them right back out. And, much of the time, the tank does exactly that. But on the rare occasion that they do not, the tank is blamed for failing at their job. A rather unfair accusation in my book as the tanks job of holding aggro is only going to be successful so long as the squishier members of the group do their jobs such that they don't cross the aggro threshold with damage or healing. Thus, a tank is culpable not only for their own legitimate mistakes but also for the mistakes of others in the party.
Really, it is much the same problem that healers face. In both cases, your job is that of enabler. You keep the tanks standing and absorbing punishment. You pick up the slack when things go pear shaped and hopefully mitigate the damage while the tanks get things under control. In either case you can do your job perfectly and the raid can still fail and you will be blamed.
The reason no one wants to play a tank (relatively speaking) and no one wants to play a healer are related. The problem is that DPS players are, on the whole, the worst sort of person in the game. Where the tank and the healer emphasize the cooperative nature of the current endeavor, the DPS game is intensely personal. People want to put up the biggest damage numbers and they simply expect everyone else to bail them out when things go wrong. It is these players who will cry the loudest when the party wipes even if the very action that caused the cascade failure was their own (They pulled aggro at an inopportune moment for the tank, the tank desperately tries to get it back, the healer tries keeping the far squishier DPS member alive which results in the tank collapsing under the (probably still) high level of sustained DPS leading quickly to a party wipe).
Of course, there are plenty of DPS players that are not utter dicks blind to the fact that they are as responsible for their own survival as anyone else in the group but thanks to the fact that any PUG is going to feature a number of such dicks ensures a tank will quickly tire of their nonsense and either stop playing or find a guild to act as a filter.