In theory it helps people who have some sort of trade and just want to do that trade, focus on that, while the business experts from the PE firm handle the business side. Running a business is a skill, and people who want to sell some other skill often don't have it as you can't be good at everything.

Are there other ways of addressing that gap, like hiring experts? Sure, but its not like PE is entirely evil.

Keep in mind there is some selection bias here. You only hear about private equity when its being comic book evil. When things work out or its a non scummy PE company, you never hear about it.