It’s easier to make friends when you’re traveling alone because, in a way, you’re forced to! You’re a human, your natural instinct is to interact with other humans. When you travel somewhere with people you already know, you have your human(s) to interact with, you don’t need to interact with anyone new. When you’re traveling alone, the only way you’re going to interact with another human (in-person) is by interacting with someone new.