I can't spontaneously drop in on people/conversations w/out an invite.

Unless I know someone really well and am very close to them, I can't just invite myself into their space. In a social way I can get involved with someone on common ground, but when it actually comes around to "invading" other peoples' space/their home, I literally have to be asked into it, kind of like the vampire chick from the movie "Let the Right One In." I have neighbors who are hurt b/c I never drop in whenever I want to. I never just 'drop in' because they never make a specific invitation--only ask me to please stop by sometime and hang out (they've asked me so many times now.) When I stay with people I don't know well, I feel like they have to ask me to be more involved with their space and their time---I feel unable to just inject myself into most conversations or activities without a specific invite. I can easily drop in on most of my family unexpectedly and always felt able to invite myself over and into the space of my past boyfriends, and a few very close friends too...but otherwise, I find it almost impossible to just spontaneously/casually drop myself into someone else's life/home, even when they've said I could do so whenever I wanted. Normal?