It's a good point, but I would say it's not awkward, just expected unless exceptional circumstances (for example two single persons sharing a flat and having similar interests at that time). Like any relationships, friendships evolve with time, you might get close at some point but things change and you are not in touch much for the next few years, and then the situation changes again and you are back closer. Don't you think?

I see this happening especially when people get in and out of intimate relationships. I think it's just life...