"Volunteers" with a sense of entitlement

I hate people who volunteer and then get mad because they end up doing all the work, when they volunteered...and then they try to make YOU feel bad for not offering...when THEY volunteered. Look, don't volunteer in the first place to do something and then get mad because others don't give you a helping hand.

Why do people "volunteer" and then get a sense of entitlement...doesn't that defeat the purpose of volunteering? Its like giving to a charity and then expecting those you give to, to pay you back later on.

It just defeats the purpose.