If Reddit has an employee on staff as a mod that can approve posts, then they lose safe harbor protections. Anything that mod approves is considered representative of Reddit, giving them editorial control and causing them to be handled more strictly. https://caselaw.findlaw.com/court/us-9th-circuit/1856011.html
Further, if Reddit gave bonuses to mods, then mods would be considered unpaid employees. Any kind of "swag" or quid pro quo for being a mod of a big subreddit increases the chances that those moderators will be considered unpaid employees by the Department of Labor. AOL famously got in big trouble for giving free/discounted internet access to their volunteer moderators. https://casetext.com/case/hallissey-v-america-online-inc-sdny-2002 (Settled in 2009 for $15 million in back pay.)
Combining the two is terrible news for Reddit and would make their business model absolutely unsustainable. Every mod would be an employee and every post would be representative of Reddit as a company. If a mod approves a link to copyrighted material, then Reddit could be sued.