I have spent a decent amount of time in France and other European countries, and I have not seen any hot tubs. That doesn't mean that they don't exist or not popular there, though. You do have to remember that most European cities have limited space inside and outside the buildings, so hot tubs are not practical. Houses away from the city do tend to have enough land for them, but you typically see swimming pools instead (especially southern France and other European countries that are further south).