I saw this and realized it had never been answered.
Ken chose his family over rock stardom.
It was at a time when he was in a tough spot, financially speaking. He needed the work. He was known for his vocals and guitar work and was getting offers from a number of groups.
Among the offers Ken got were Foreigner, Deep Purple, Motley Crue, Peter Frampton, INXS, Journey, and Black Sabbath.
The deal to take any of these jobs was: 5 year contract, 9 months per year on the road, Two months per year in the studio, and one month per year off. Ken grew up as a teen without his father in the home (I use the term "home" loosely, as things were kind of rough, and not too cozy). Ken's son was 13 at the time and his daughter about 15. He did the math and realized that he would be doing to his family what had happened to him. He would be back about the time his son would graduate from high school. Ken said no, and took another, harder, less in-the-spotlight path and stayed to be with his family.
This would be a hard choice for most of us. Ken is a man of integrity, and he made the only choice he could make in that situation.
They're only kids once. Every day counts.