Its the best thing to do if you want to make a lot of money from your money machine and are largely apathetic about the outcome of the business itself. Easy enough to find the next MBA graduate to feign passion for you while they are just trying to sell the company.
Because employees actually gain out of it. That's also a benefit as it gives more people financial freedom and they can go off and do their own companies. Instead these people get locked in to AirBnB for years.
Private companies even issue bonds on public bond markets, these can be as large or larger than equivalent equity offerings on the stock markets.
Don't let the mechanisms pursued by a handful of VC firms in Silicon Valley distort your understanding of capital formation.
https://www.cargill.com/about/financial/credit-rating-inform...
It's one route to take, but not the only one.
That would be through an IPO or acquisition, either way you loose control of your company.