This sounds like me a bit I think for me its just I have to put in 100% and I guess other people don't as much. prime example I have to give the perfect gift takes me ages, and on my friends birthdays I usually send a really nice email as I don't get to see them I put thought in. I usually get a text if I am lucky meh I have gotten used to it.
The thing is last year on my friends birthday I didn't write her an email or do anything I would normally do, and just wrote on her facebook wall (yeh I know lame, but I was in one of those places where it was like I dont give a f*** as everyone else doesn't which is so unlike me!). She got quite angry at me didn't talk to me for a few months and me being stubborn didn't try to make things up (I know childish), and yes it was I who caved in and made the first move. Later she told me she was hurt that I didn't make an effort for her, but she never makes an effort for me. I don't want to lose 10 years of friendship but clearly it didn't matter for her!
Its just I value friendships quite highly as I only have a selected few, and I've known them for years. The thing is what I am holding onto is the friendship we had way back then, they are not the same people but for some reason I cannot let go!
You sound like a great friend! But everyone is different!