Because public companies get a huge infusion of cash from their IPO.

This makes them a much bigger fish in the pond.

Big fish eats the little fish.

Grow or die.

The kind of core problem with a market based economy is that markets almost always tend toward consolidation over time… and you have to have a well maintained set of regulators and laws to keep up with industries to keep this in check.

But those corps tend to have so much money and influence that they just buy the government via outright bribes/corruption and PR campaigns to dupe the masses into supporting politicians and policies that will be corpo friendly.

In short… most companies actually are private. 9/10 new business fail in a year or two, largely because they cant compete in a world dominated by a small number of very well known, very big fish.