They are invariably, actually, not very valuable at all beyond the fruition. Take a look at any Forbes or FT top 100 list and see how many of those companies are being run by founders.

Companies go through a lifecycle of change before they reach anything resembling stability or a pace of business that isn't completely volatile the people in it. During that time the types of people that the business need to achieve the goals of that lifecycle stage are very different.

Steve Jobs types, on the other hand, are actually extremely rare and the exception rather than the rule.

Founders are big thinkers and risk takers. When a company has found success, the owners prefer to focus on scaling that value rather than doubling or tripling down on the next big thing but the founders often want to keep betting it all.

Put another way, if you bet 100 and have turned it into 1,000,000 would you want to get your money out or play roulette?

It's not a matter of reward or punishment. It's a matter of the skills required for continued success.

Early startups require big risk-taking, progressing at an absurd speed, charisma to get investor capital, and really just being a little crazy.

Once the concept is proven to be viable and potentially profitable, the focus needs to shift from proving it can work to making it sustainable. This involves less risk, process improvements to avoid issues like getting sued, better money management, more careful time management to avoid burnout of non-founder employees, and generally just being more rational about things.

It's rare that a person can exhibit both of these sets of behaviors, so companies will often swap out the former for the latter as a company matures. If they didn't, the founders might unintentionally drive the company into the ground by taking unnecessary risks after finding something that already works.

Does that answer your question, or did I miss the mark, still?