Mods voluntarily do their job, so you should, too.
Although moderators do volunteer their time to support the website, they are paid for their work. IIRC 25% of the forum's income from ads is split among the moderators, and they're paid according to the work they do (so a mod of 15 sections would receive more than a mod of 3 sections).
That's true, they get paid to do it, plus there's added bonus and perks around for members of the staff.
I guess that's why some people desperately want to become one.
As far as getting something as reward for reporting, i think it would be a good idea, but not in form of activity points as OP wants.