I think there is another possible reason of the "all kinds" answer. people don't like being pigeon-holed as the sort of person who likes a aprticular type of music. They don't feel their tastes can be encapsulated in a couple of sentences and a lot of the artists they like are fairlt unknown.

At least thats a reason why I have given that sort of answer in the past - especially where I have got the feeling that the other person is just making polite conversation, or seem to like completely different sorts of music to me.

Bagpuss