It happens easily at highway construction sites with narrow lanes, on narrow streets in the city or when parking. Two vehicles touch each other – the mirrors fold away and the glass breaks.
You do not have any rear sight anymore and without a functioning exterior mirror, you are not allowed to drive on. If you continue your journey nevertheless, you do not only risk a penalty, but you also might face legal consequences with your insurance company. Your insurance company could take you in recourse if an accident happens. Apart from this you would extremely endanger other road users, since you can not see what is happening behind you.
You have to leave your vehicle or call the breakdown service. This is not only expensive, but also very time consuming.
And if you are on holidays in a foreign country the problem is even worse since very often expert help is not nearby.