Is it simply because the metrics are so obvious (i.e., attribute sales to the salesperson's individual performance), that it's easy compared to other roles?
Is it because sales work is so close to revenue numbers, that more thought has been given to compensation, or it's thought of differently (like CEO comp)?
Is it a belief that the personalities of salespeople in particular are motivated to perform better by the incentive alignment?
Is it because performance-based can be a sweeter deal for high performers, which some historical salespeople managed to secure, and they're not giving it up? (Should SWEs be maneuvering to get "points" on the particular products they worked on, rather than it just being something they can mention when they beg for a promotion?)
Something else?