There is also the common case: I hit a problem, search th internet and find tool X. I give X a try, it solves the issue. I move on. Or I give X a try, it doesn't solve my problem, so I forget it and try elsewhere.
The simple fact is, most people have come to expect that submtting feedack on a free project is unlikely to resolve any issues they have in the immeadiate timeframe, if ever. And if they aren't having problems, they have absolutely no motivation to provide feedback because whatever problem they had is solved.