I am probably the person receiving the most ref test requests and denying them. This is probably because I'm on AIM a lot, but hardly am ever able to do tests or ref, because I'm usually doing homework.
I don't think the pay is the problem for basic battles. They are the easiest battles to ref and give out a decent amount for almost nothing too intensive. Maybe how boring they are, or having to post over and over, or writing logs are the problem.
For me, it does not really matter what kind of battle it is, but if I am able to do it at all.