They already have this and, according to some insiders, it's part of the problem.

Basically the claim is that quantity of edits makes it more likely for you to "level up" within the Wikipedia community. This count includes reverts of perfectly good info as when you optimise for any variable, people find ways to play the system.

They also do simpler things like force you to sign up to create a new page, as opposed to edit an existing one.