This seems downstream from the single vs. sharing your life with someone. I don't mind traveling and doing cool stuff alone, but every time I do, I start thinking about how much better it would be to do these things with someone. Unfortunately, my romantic relationships hardly ever line up with points in my life where I have the time or means to go do a lot. Having good close friends is a nice second to having a good relationship. Point is, yeah, life's hollow without people to share it with.