We live in a world where people are empowered to feel a sense of entitlement. When anyone threatens to take away this security blanket of "it's my game, I'll play how I want", they get defensive.

Not everyone responds the same way, but it does seem to be a common issue as far as people underpeforming and being unwilling to improve or accept criticism (constructive or otherwise). It seems they would rather remain ignorant to the fact that they actively affect how others are able to experience the game in a group setting.