I don't like to travel alone either and think it's a lot more fun to travel with a good friend who's down to hang out, has money to hang out, open to new experiences, but also not too crazy that you have to make sure he/she doesn't get into too much trouble.
BUT
If I couldn't find anyone to travel with me, I'd go alone too. There are some places I'd be less inclined to visit solo, such as, let's say, Thailand or Malaysia because I feel like I'd need a "local" to guide me and shit. But when it comes to the US and Japan, these are such popular tourist destinations and well-developed that you don't need anyone to help you with anything. Also, it's incredible how down-to-earth travelers are and the extent to which they're down to hang out. In other words, you can easily make friends and go sight-seeing/whatever with others wherever you go. Point is, don't let lack of companionship for traveling deter you from traveling.