Hey Christina,
I totally understand! I do that as well, give my feedback, hoping that they'll notice their scores went up and then give me mine. Some things I can say though, depending on what you're selling:
You usually won't get feedback until after someone has received the item.
You usually won't get feedback until after someone has used the item.
Some buyers are new and don't even know how and where to find the feedback.
Some buyers just honestly forget.
Some buyers just honestly buy and that's about it. No feedback, no anything.