The vote selling economy on steem is not a valuable niche

I'm quite sure you misunderstood my intent here. I meant valuable in the sense that people can make money doing it. I didn't mean valuable in the sense of valuable to Steem overall.

Yeah sure, if they're allowed to

You should better understand what the permissionless property of blockchains means. No one needs to be 'allowed' to do anything, they can just do it. The only way in which it can be stopped is by changing to system rules and incentives to make it a smaller or non-existent niche.