What do you guys think is the cause of severe lack of Tank users?

[MistakeNot]

This is true because when I heal and see the tank doing slow pulls I usually pull a bit more for them. They don’t need to worry because I’ll keep them alive.

What makes you think that is why they did not pull more?
When I tank I really hate if other people pull extra mobs. Too many mobs means that I can't keep track of where all of them are, I can't avoid their AoE attacks, I may have trouble keeping aggro on all of them and won't notice if some get away from me.