Upvoting a post releases the Good Chemicals in the brain. You do this when you would like the person who made this contribution to do more of that.
Downvoting, in turn, produces the Bad CHemicals. The downvote button was famously invented to replace the previous disincentivizing mehchanism, Hammers.
On the one hand, embrace-extend-extinguish is a classic playbook for big evil companies.
On the other hand, it remains to be seen if anyone takes Meta up on a new offering. I'd have complete faith in the future of the open Internet if it was Google trying this.