When it comes to spending money, I can sympathize and I do not expect people to shell out cash that they don’t have. (Indeed, when working on a free software project I hope that occasionally it finds its way to someone that literally could not get it any other way.)
On the other hand, 2-minute acts of appreciation (that cost practically nothing) are also extremely rare. Why should thank-you E-mails, app ratings, etc. come from a vanishingly small fraction of a user base, instead of almost everyone?
Because majority of people have no idea you want email with thanks and figures that best thing they can do is to not bother you. Like celebrities complain about people recognizing them all the time.
On the other hand, 2-minute acts of appreciation (that cost practically nothing) are also extremely rare. Why should thank-you E-mails, app ratings, etc. come from a vanishingly small fraction of a user base, instead of almost everyone?