Need. Not really. It works more on the idea that if you can you should do something, if you can't that's okay and you'll probably be on dish duty unless you sneak out toward the end of it.

[ spoken like someone who has seen someone do that. he will never say who. ]

Some people go every day, some are like me and I only go to it once a week-ish? Some people don't go at all. Which is dumb of them, but whatever, they suck.