While this makes several cars a terrible choice for rentals, I do wish car owners would take maybe half an hour of their day after spending a couple thousand to read through the manual that came with their car. The manual doesn't just tell you how to change the radio station, it also contains a lot of safety information and instructions for how to act when something goes wrong.
How can I trust a driver to take things like safe maximum load into account when they don't even know they can open their car if their battery ever goes flat?
Because cars have had consistent keys and doors for how many years now? That's half the thing about cars - you shouldn't need to read the manual to know how to open a fucking door. Maybe for service timings, etc, but you should be able to get into any car and be able to use it for completely normal use cases *without* reading a manual.
And often there are useful things that I wouldn't know otherwise.
For example (Kia Carnival): Holding the lock button on the fob for 20 seconds will automatically close the sliding doors and any open windows.