Not sure if previous Forzas had this. But most other racing games that have a rivals system on a weekly/monthly schedule have a payout based on your final finishing position (Gran Turismo, Dirt 2.0, etc). If they want to attract more people to rivals I would think they would give some rewards. I don’t see the point of driving lap after lap for an hour and a half to not get any payout if you finish really well.
As we know, credits in this game can be a little rough to come by if you’re trying to buy lots of cars. And you can earn them more quickly by replaying the career modes (albeit pretty short and repetitive) as you get cash for practice and the races, as well as car XP.