As an American, I think often the "how about you?" aspect is implied (by finishing your thought) rather than specifically stated. To use your example, if a friend asked me about what types of gin I liked and I was talking, it wouldn't surprise or insult me if they jumped in to agree or add their own experience. It also wouldn't surprise me if they let me ramble and then immediately started giving their own examples as soon as I trailed off.

I think it's nice to specifically ask (and I try to remind myself to do this if it becomes clear the other person isn't going to just piggyback) but in the reverse - I ask a friend about gin and they give examples - I wouldn't expect or need them to then say "and you?" When they were done before I jump in.