Not everything in a country can run by a government so which itself enough why we need private sectors to keep things in balance, of course government bend their rules in favour of them for whatever reasons while private sectors create job opportunities that again help someone to make money and they will spend the money they earned so that will obviously help in the development of economy in a country.
If people are honest, the government would be enough to provide whatever the people in that country needs, private sectors are just businesses that want to make money because not all of the things that many people ask for can easily be provided by the government. Most people want more than others and so we got ourselves a capitalist economy and it just so happens that when you've got wealth, you can buy power and influence, that's probably a reason for why we have these private sectors, that's the end goal for most of these people anyway, to create a lasting impression and legacy.