I think you're making an economic argument, the counter to which is
"the cost of the plane rental is higher".

I suppose it's economic; it's more a "pain in the ass to the FBO" argument. If somebody has to come out of the office and do a walkaround with every pilot both before and after they rent the aircraft, the time required can add up quickly. It is not inconceivable that an extra full time employee would be required at some outfits just to do these inspections. Yes, the price will be higher, and the availability will be lower, since the pilot will have to wait for an inspection before getting the aircraft, and on return, before going home. This would be unpopular.

[as an alterntive] If the pilot fails to report
a problem that is squawked by the next pilot's preflight, then this is
presumed to have occurred on the first pilot's flight.

As you point out, the problem may well have occured four flights ago and manifested itself two flights ago.

While this might seem unpleasant at first, if it improves the market for
leasebacks - and therefore increases the size of the fleet of rentals
available - isn't that a Good Thing?

Yes, all things being equal. But they seldom are. It will mean a diminishment in rental pilots going to that FBO, and the ones that leave may not be the ones you'd prefer to leave.

The FBO knows its pilots and its leaseback owners. They can restrict aircraft rental, and they can talk to the leaseback owners too, who can do the same. But that's money that goes to another FBO.

You may not get what you pay for, but you sure pay for what you get.

Jose
--
"Never trust anything that can think for itself, if you can't see where it keeps its brain." (chapter 10 of book 3 - Harry Potter).
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