Then they sell them off after accumulating 10,000-25,000 miles, before any real maintenance is required.
20,000 miles is what, 4-6 oil changes?
Interestingly JD Power claim that EVs have more problems https://techcrunch.com/2022/06/28/jd-power-evs-and-and-plug-... .. but mostly in the infotainment system? Maybe that matters less to rental drivers. Maybe that depends on brand.
Most new cars have a 10,000 mile factory oil change interval. PHEVs usually go for 20,000.
Rental cars sometimes have a hard service life, but I'd put that range at maybe 1-2 changes. Which isn't much at all.
More likely there's a usage difference; if you're puttering around from the airport to the hotel and back, you might pick an EV, but if you're renting a car to drive a longer distance one-way trip, it's mostly going to be an ICE, and you're gonna put some miles on it at high speed, etc.
Minor clarification: Highway miles are actually gentler than city / town miles. Less wear and tear due to stop and go traffic, 90 degree turns, and fewer potholes.
But mostly the observation is that you'll likely get a lot more miles on the car in such a rental than a local rental. So a rental company that keeps a car in their fleet for 2-years or 20,000 miles is going to likely send most EVs out for age and more ICEs for milage (in my estimation, anyway), and so sure, ICEs will have oil changes in that interval, but they'll also have more of the every car needs maintenance sort of proportional to use (runtime and/or mileage), because they'll see more use.
And on top of that the average EV probably has low(er) rolling resistance tires (to get a few more miles of range) which get replaced every 40k instead of whatever sticky tires the OEM slapped that only last 30k so you're doing that routine less too.