They can be social fun, but never confuse them with entertainment. They're not for people to listen to, but to join in with.

Personally I prefer a good tune session to a singaround any day, because a) it's a lot easier to join in and learn something quietly when everybody is playing all at once and b) mostly everybody is playing all at once, which is even more inclusive social fun than sitting around waiting for your turn. Oh, and crap singing is far far worse and more embarrassing to sit through than somebody playing badly, buried in a tune-up.

Make sense?