sMerit is limited. I have a responsibility with it. I can use my sMerit to reward good posts, incentive good behaviour with that (publicly shown) reward and help make this forum a better place by increasing the post quality.
Or I can sell it (likely be banned for doing so), incentive spam and contribute to the already very evident problematic of shitposting.
I cant do both, as I have limited ressources. I have to decide, and if I care about this place, this is an easy decision.
Yes, selling trust is also a problem. However, it affects a smaller sub-set of users who use this forum to trade.
Selling sMerit could potentially be a bigger problem, because a lot of members use forum activity ranks for airdrops, bounties, etc.