This is true but having lots of small public investors sometimes makes it easier to maneuver than a handful of big fish / massive investors akin to many small customers compared to 1-2 big clients that dictate your fate.
Public markets are similar to product development that targets many small customers compared to private markets that are like services / contracting that have a few or one big client, the latter is more risky and sometimes you are directed by the big fish rather than not being worried about having to please everyone.
Public markets are directly tied to everything now, the stocks, bonds, wages, jobs, retirement, funding, etc. Equities were created to give everyone a chance to invest and ride the tide up with the big boats, if companies are already tapped by the time they go public, public markets, retirement and market based wealth will not be as robust.
Today, it's also prone to sudden random fluctuations because an algo-trading software Bayes classifier decided to sell based on historical data it pulled out of its shiny metal ass.
What other reason is there for an IPO?