Let's take your assumption to the end result; the developer has no control over mod distribution. Let's make up a hypothetical (which has happened before) where someone is distributing malware with their mod. Does the developer have no authority to take it down?
Mods, whether you like it or not, do reflect back on the developer. If there's a scandal of bad behavior, it'll effect their sales. Also, if payed mods become the standard it'll effect their sales, as people will be less likely to deal with modding. I have no issue with mod developers making money from their product, but they must also recognize that it's with the support of the developers of the game. If they decide to remove your mod they can, in many ways.