Many English speakers believe that wherever you go on holiday you can communicate by speaking English, so there is no need to learn any other languages. They think if people don't understand you, all you have to do is to speak slowly and loudly. You can do this when you stick to popular tourist resorts and hotels. You can usually find someone who speaks English there.
However, if you want to venture beyond such places, to get to know the locals, to read signs, menus, etc, knowing the local language is necessary. A basic ability in a foreign language will help you to 'get by'. For example, to order food and drink, find your way around, buy tickets, etc. If you have a more advanced knowledge of the language, you can have real conversations with the people you meet. That makes your holiday more interesting.