I found that a very good way to put things.
In a gift culture people participate by giving in one form
or another. It is fun to answer questions. It is pleasant
to get questions answered. It is satisfying both to go from
asking to answering and doubly so to help others do
likewise.
But people who essentially say, Gimme! aren't as fun.
If you clearly do not appreciate that you are asking for
my time and energy, then I am not going to want to give you
any. By default I assume that people do understand
that this is a gift culture, I don't assume that people
are thoughtless. But if they truly are, then no, I do not
have to answer their questions. I am not paid, I have no
obligation to answer questions...