Without feedback you don't know that the bug was fixed in reaction to your bug report. It might have been - but unless they explicitly invited bug reports in return for something then it's at worst bad manners not to acknowledge in that case. Debatably poor self-interest on their part as well.

As you note, the field has been damaged by bounty hunters. When the SNR drops low enough there's no point even reading the damn things and high-quality reports will be discarded along with the dross.