The way I see this is that at the end of DS, both MK and JI had enough, the band was too much, too big. They had to call it a day, and carrying on working together would have not been a clean break. So Mark went on to a build a succesful solo career and John stopped making music for a living and went on to express himself in other ways (painting).
They simply went their separate ways, naturally. I don't think there is more to it than that.
If Mark was looking for a bassist (and when you have Glen Dorf in your band, you don't go looking for somebody else me thinks...) , or a guitarist (again, when you have Richard Bennett in your band.... say no more) and John was available, I don't think there would be a problem in them working together again...