"Those persons who cannot work alone,who must always be surrounded by companions,who do not instinctively prefer to train and practice alone,or as near to being alone as possible,such persons can never expect to achieve the successes that otherwise could be theirs," a quote from Success in Sport and Life by Percy Cerutty.
The above brings to mind a few things as it pertains to people who are seriously committed to running. First, I think we've all known people who would rather not run then go for a long run alone. Some have told me it gets "boring" when they're out there for several miles and they don't have someone to talk to. I believe a statement like this shows, to a certain degree, a lack of mental toughness and discipline. We are increasingly becoming a society that is continuously surrounded by sounds,be it music or someone talking. It should be a welcome relief to be able to engage in something where you can be alone in your enviroment and thoughts. I've heard runners tell me that they do their best thinking when they are out on a long easy run.
Others have told me that long runs,alone and away from traffic,provide a contemplative aspect to their running.
If you are indeed serious about your running,do not ignore the necessity and benefits that can be gained from running alone.