I believe Lyft has a rental program. From what I've heard, it's basically indentured servitude for the drivers.
I heard at one point it was like $400 a month but that included mileage and you weren't locked into a long term lease. The ones sitting on the lot may be the drivers that got out after not making enough money.
I also heard that there was a reason some drivers didn't have cars and the accident/loss rate was higher with those drivers so those programs may just be winding down which may also explain the cars on the lot.
Lyft has a deal in place with Hertz, but they also have something called Express Drive. You pay Lyft $200/week, you get a car with maintenance and insurance included. There's a Lyft Express Drive/Rental depot in my town and I've seen mostly Hyundai Elantra/Sonata there.
Uber works with Enterprise but they have a similar plan with Fair - get a car on Fair as an Uber driver, pay $200/week. You get some flexibility on cars, I've been in Fords, Nissans and Hyundais from Fair as a passenger. Same deal - maintenance through Pep Boys/Aamco and insurance provided.
Lots of Uber/Lyft drivers don't have good credit - most of them bought new cars on subprime notes. The local Toyota dealers here were wheeling and dealing on Prii and used cars for Uber drivers.
most of the ones i saw were 2017 elantras with 80 -85k miles. the insides were pretty dirty . seems like the cars came back and the lot did not even bother to clean them before they put them out for sale.
There was an article on Bloomberg or Forbes saying the best/only way an Uber driver can make money is to buy a 2nd gen 2004-2009 Prius instead of the $200/week rentals.
But a Prius is a time bomb when 150K rolls around - battery pack, brake actuator and on the 3rd gen 2010-2015 models head gaskets. With the money a driver saves instead of leasing a car, that money could be pocketed into a fund to replace two of those things. However, in some cities, you have to get commercial insurance(or a TNC rider on your personal policy) and a business permit to be legit.