I'm naturally an introvert, and according to 16 Personalities I'm an INTJ-A if you are into those kinda things.
I like being alone. I can be couped up in my home alone for days and not get cabin fever or feel the need to talk to someone, yet my background is sales. I'm not antisocial nor socially awkward... I just "recharge" when I'm alone and not interacting with people.
Traveling without a companion or coworker is time where I can reflect, evaluate, game plan and strategize both mentally and on paper. It's nice to not be bothered during this time as I am constantly interacting with others when I'm not doing this.
I think of traveling alone as a time to recharge and be even more productive, even though I'm not truly alone as thousands of people are around me in airports and hundreds on a plane.
It's amazing how much I get done when traveling alone and how much better I perform after I've been traveling.