In my experience it's the opposite.
I have a fairly new account (sells different stuff from this one) which has had over 20 sales, FB left on shipment, and only five FB from customers.
It's annoying when you are starting out. But FB is voluntary.
It can be useful, if you are deciding who to buy from, all else being equal, to see if the number of FB the seller has left is greater or smaller than the number she has received.
We posters often advise new sellers not to ask for FB, because they might not like what they get.
Since sellers can only leave positive FB for sellers, you could send your sellers a polite message asking that they help you build your reputation here by leaving you FB. The worst they can do is ignore you, which is exactly where you are now.
BTW, some members leave FB in batches once a week or once a month. So there's that.
