There's a great discussion about the perceived benefits of sticking with the founders or firing them from the board's / VCs perspective:
"Looking at the abrupt change in skills needed in the transition [from early stage to large company], it’s tempting for a board to say: Maybe it’s time to get more experienced executives. If the founders and early executives leave, that’s OK; we don’t need them anymore. The learning and discovery phase is over. Founders are too individualistic and cantankerous, and the company would be much easier to run and calmer without them. All of this is often true." [...]
"Time after time, startups that have grown into adolescence stumble and succumb to voracious competitors large and small because they have lost the corporate DNA for innovation and learning and discovery. The reason? The new management team brought in to build the company into a profitable business could not see the value of founders who kept talking about the next new thing and could not adapt to a process-driven organization. So they tossed them out and paid the price later."