I go /out/ alone all the time.
The first reason is that I don't have many friends to begin with, and even fewer of them go /out/. Those that do aren't the type who I'd expect to bicycle 6-8 hours a day every day for days/weeks/months straight.
The second was described well by
>>114456On my own, I go when I want, as fast as I want and stop when I want, for as long as I want.
Would it be safer with a friend in the middle of nowhere? Sure, but it just isn't as practical.