> Uber doesn't really have a way to increase profit through messier cars

Don't they? Allowing messier, older, and less pleasant cars would increase the supply of drivers, allowing Uber to place lower bids on those drivers, lower their prices, increase volume and revenue, and increase profit.

They can definitely have more beat up cars which over time I can observe in my city. As for prices, luckily they have a lot stronger competition with bolt and local taxi apps as creating a local taxi app is really not that hard