Not all merit sources are created equal. Some get low double figures of sMerit a month, some get around 1000, and everyone has a variable amount of their own sMerit left as well. The ones who give out several merits per post as standard do that because they can. If I tried to hand out that many, I'd have to merit around 10x less posts than I currently do.

If I run out of sMerits by giving 1 merit to lots of good posts, that's fine, but if I'm down to my last few sMerits, then I'm not going to give them all to one post (unless that post is exceptional), and leave myself unable to merit any other good posts I see until I get refilled.