Hmmm... this is/was only a UK issue. I am familiar with the Mercedes key. The Renault "key" is even more radical; it's a card that you insert and you press a start button.

More conventional key systems (e.g. Honda) usually offer a "valet key" that has no fob and prevents access to the trunk.

Luckily my dream car was discontinued in 1995, so I don't have this problem.