While I agree with you that it is less safe than hiking in a group... I don't think it is unsafe by any stretch of the imagination. I work in an office and I tell people all the time, the most dangerous thing we do is sit and stare at a computer all day. It would be interesting to get statistics on the dangers of hiking vs. hiking solo. I've never seen anything along those lines. Like Glen, I think the most dangerous thing about hiking solo is the drive to the trailhead.
Too little physical activity or exercise is life threatening in the long run.
The risks of solo hiking depend on mental and physical fitness, age, survival-knowledge and -experience, equipment-quality, preparations, carrying a radio for weather reports, distance, weather, terrain, bear threat, etc.
If the friend at home does not know EXACTLY how and when to call in search & rescue, there is a good chance, that he will wait a few days too long, to do so, fearing to be held accountable for an embarrasing false alarm.
This friend at home should also know the color of your tent and clothing. And one should know beforehand, who will pay for expensive S&R in case of such false alarm. http://diaryofawanderess.com/is-hiking-solo-dangerous/