It is very interesting to read about why some people would never tour alone, because this contrasts completely with my own preference--I always tour alone.
Solo bicycle tours and backpacking trips, for me, are an important means to recharge my mental batteries. My chosen career often brings me in contact with many, many people and I need time away from humans. However, on a bike tour, unless I was riding in an extremely remote area, I have never really been completely alone. There are always people around and many are interested in the journey. Finding people to talk to isn't difficult if you are a normally social person.
I tend to be fairly introverted anyway, so my conversations with strangers normally don't go very far. Feelings of loneliness will happen if you are traveling solo, so it can be important to make sure your mind is occupied. Keeping a detailed journal, reading, and nature observation are all vital activities that help keep my solo tours enjoyable. Without those activities, my evenings could easily become boring and lonely.
Touring alone is safe and fun. I wouldn't do it if my experiences told me otherwise.