Hidden interface controls that affect usability

    The other day I was locked out of my car
    the key fob button wouldn't work

    Why didn't I just use my key to get in? 
    First, you need to know there is a hidden key inside the fob.
    Second, because there doesn't appear to be a keyhole on the car door,
    you also have to know that you need to disassemble a portion 
    of the car door handle to expose the keyhole.

Hiding critical car controls is hostile engineering. In this, it doesn't stand out much in the modern car experience.

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?

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.