There are many upsides. As a loner I write from experience.
1) You are free. When you travel you don't have to consult with anybody about what to do. You can do whatever you like, whenever you like, however you like. If you see life as a journey, although it's a flawed metaphor, the traveling philosophy can still be applied somewhat.
2) You have minimal contact with people, and all their bullshit. Of course they have their good sides too, but at least you're free of the bad stuff, which is saying something.
3) If you actually like Saturday nights alone watching the fights, drinking your favourite booze and eating your favourite food, undisturbed, no responsibilities other than to relax and enjoy the fights, then there's nothing wrong with you.
4) You don't have to concern yourself about offending anyone, pleasing anyone, anyone's approval, anyone's judgment....you can just be yourself. And in the big picture, when you're "yourself" you tend to follow along the path that is meant for you, as opposed to veering off in directions that others think you should go, or that you think you should go to please others.
5) You learn how to be self-sufficient emotionally and practically. That can come in handy later in life especially.
6) You can become a teacher to those who are lonely of how to be a loner without feeling lonely all the time.
7) You can focus on reaching a high level of spirituality through meditation and reflection, if that sounds appealing to you. All of the great monks have been loners.
8) You have more creative space.
9) The "outside world" is fucked up in many ways. As a loner you're less involved in it, as it's people who make the fucked-up world go 'round. Maybe this is the same as 2), so maybe I'm done here....oh yeah, one more....
10) I like bagels. (Just checking if anyone got this far.)