Because nobody knows anything about most companies and when they 'go public' nobody will buy their shares. The classical IPO process involves a road-show where

Because nobody knows anything about most companies and when they 'go public' nobody will buy their shares. The classical IPO process involves a road-show where the banks take the CFO/CEO to institutional buyers they line up ahead of time, they work out a price agree to buy shares ahead of time for a set price. The process is underwitten by a bank(s) who buy the shares ahead of time for a set price thereby providing certain guarantees. This notion of 'leaving money on the table when the stock pops' is just frothy hubris: the stock could equally flop, moreover, if somehow every share were sold first thing in the morning - a 'stock pop' would not benefit the company directly anyhow - the stocks will have been sold. An IPO is a big fat financial service offered by the banks, for most companies that's the path to market. Avoiding it would probably require a big brand name company with a lot of recognition, probably a very big price. Even then it's risky.