The direct reason for PRs is to give OoS players an idea of how people place in case they don't follow the region. This is especially significant when players are looking to MM the top players at a given tournament and need to prioritize their time. Indirectly this recognition is considered rewarding to some players, and as a result it can serve as an alternate function for motivation.well PRS are based on tourney placings, not MM's unless they are PR MM's and those are done rarely. So I would think tourney placings show skill and MM's are just a void to gain extra money on the side or to practice a bit.
I don't know about SFL/NFL, but in CFL the primary/common purpose for MMs is to gain experience/practice and -- in the case of OoR -- to gauge your skill.
For some personal examples, I'm money matching Pesticide for experience, DJ Jack as a friendly gesture because I want to play with him and I know that he wants to money match me, and I would money match ESAM if he were coming because I want to see how I rate against one of the best players in the world -- even though I know that I'm bad at this game. Notice how none of those are for the purpose of making money. I have a job for that.
I understand how you might see MMs as an opportunity for income if you don't have a job, but if that's the case then you're better of partitioning your time for job searching, because the only Brawl player in all of Florida who has turned a profit for the past couple of years is ESAM, and even then he is probably is cutting even from all of his pot filler days. You can't expect to be making bank off of Smash when players like Mew2King are struggling to make a decent standard of living. Players like me, GDX, and Seibrik extensively travel in-state, OoS, and both, respectively, but we all have something in common: We work and earn money outside of Smash.