crass to ask for feedback after a transaction?

i have been building a system for the last year, and have bought almost everything on audiogon. somehow, i have had extremely fantastic luck, in that the folks i have bought from have just been the absolute nicest people, very willing to answer questions, and freely sharing info and their vast knowledge. really coming out to help me learn more about the equipment we all share such a strong love for.

as a new member of the community, i can see the importance of the feedback system. i have always left positive feedback for the people i have dealt with. so far, two members i bought from have not left feedback for me, even tho i know they are sent a notice when my feedback is submitted, and even though we got on well together during the course of our dealings with each other...

in terms of general politeness, positive feedback would be much like a compliment, which one would never want to solicit, or "fish" for. in the context of our community, or "family", if you will, feedback could also be viewed as a courtesy, tho it seems as though the folks who established this system for us expect that we will do this small thing for one another.

do you think it's crass to ask a person to submit feedback after a transaction? i wonder why it seems not to occur to some folks, who seem completely nice and polite in every regard? ultimately, does it truly matter all that much?