YES plenty of buyers don't leave feedback.

NO don't ever hassle a buyer for f/b. It is completely voluntary so neither one of you has to leave it.

If you want to increase your f/b score then I would suggest you buy a few inexpensive items.

Don't stress over f/b - if you're selling a good product and offer the best service that you can, your f/b score will eventually reflect this. We all had to start from zero - you just have to be patient and slowly build a reputation as a reliable and honest seller - it doesn't happen overnight 🙂