How come some of my friends can't make eye contact with me when they are talking to a group of friends? They only make eye contact with one person the whole time, and I find it rude.

I know what you mean. I don't think it's on purpose.. First try joining in the conversation more. If you're doing a lot of listening, and not much talking it could be why. If it's a close friend or If that doesn't work tell them straight up. Jokingly say something like "Yo, you know when you're telling a story you only look at one person? Haha" I doubt anyone has pointed it out to them.