Why do people do this?

[Eddy]

I know how it feels bro. It would give you some closure if they would just decline right? Maybe they're just not brave enough to outright decline you because if they have to see you in person it might be awkward. So they just pretend not to see it and forget about it. Best you can do is give them some time to accept. If a considerate amount of time passes and they don't, you can always cancel your friend request. If they think you're not good enough for their FB page, so what, it's their loss.