Could it be because he doesn't feel good enough for you as a friend so he compensates for his inadequacy with gifts/favors?

I admit, I am like that so I can understand where he's coming from. I have a hard time making/keeping friends so I tend to go out of my way to keep what few people I have in my life. I ordered one friend pizza twice in the last month and I'm planning on building another one a cheap gaming PC for free soon. I even risked homelessness a couple of years ago just to get my former best friend away from an abusive relative. I am this way because I don't think I'm good enough to have people in my life so I am overly generous to reduce the chance they will abandon me later on.

Maybe this relates to your friend somehow?