Can anyone explain why I've lots of friends from a distance?

My birthday is remembered by about 13 'friends' (and vice versa). I send and receive about 50 Xmas cards, I get occasional phone calls (after I to ring them), I have a lot of friends at work, but no one ever wants to come to visit me or I don't get invited to them. People like me because they tell me they do. I never get any support from anybody, even though I offer my support to them. Can anyone explain why?