This is my impression also, there is usually explicit "only customers" where there are genuine problems (overtouristic etc) or where the boss is just weird (eve

This is my impression also, there is usually explicit "only customers" where there are genuine problems (overtouristic etc) or where the boss is just weird (even though you may be still told off even without a only-customers sign in some cases). I would say most of the time, under normal circumstances, there is no issue. Even then, I cannot imagine somebody saying no when telling them "I have a health issue and need to use a toilet", in most cases.