Well because they love their job and don't want to become some kind of manager BS, be responsible of other life, be tough or whatever, suffer from their employee (I want more money, I want to do less, absenteism, trials, lack of motivation, lack of talent, harmonisation hard to maintain...).
Most people I know with small companies are tired of their employee, and wish to have something smaller.
It has been discussed a lot and well I understand their way!