One thing to note is that in Europe, they tend to break out the insurance cover - i.e. in the US, there's only one insurance that covers everything and you either take it all or take none.

But in most countries in Europe, you can get CDW (for collisions), Theft insurance (for uh, theft), and Window/Tyre insurance (for damage to windscreen and tires. CDW is normally included for European renters (with a high excess), as most European credit cards do not provide car rental insurance, but the other 2 types of insurance are optional "extras".

This is why the check-out people tend to be much more strict about damage to windows/tyres, because this is a source of revenue for them - the more strict they are, the more likely you would buy the insurance (which is a rip off, but a separate story).

For them, they don't seem to understand the concept that the credit card will cover that damage since European cards don't have that benefit.