Sometimes being around people you've known for a long time is very emotionally taxing and for me at least, they become linked to a particular time, emotion or event that just becomes too hard to deal with. A lot of times its easier to be around people you don't know so you don't feel like you have to put up a good front or try extra hard to feel when feeling hurts so much. Its not that they don't love you. Feeling can just be scary sometimes.