Nice to meet you, Brer Quabit! Welcome.
Off the top of my head I think there are two reasons people aren't committed. One is they don't really enjoy it. The second is they think it's not important. For example, if it's not fun maybe it's because they don't like song choices or they have a problem with the leader (that power hungry egomaniac!). If they don't think it's important maybe they haven't had good teaching (pastoral support?) on why we sing and play, or maybe they're too into their kids' Sunday morning soccer games. If you can define which of these is true of your people, you'll have a shot at overcoming it.
Oh, and don't you quit. Remember Who YOU are playing for and WHY.
