Not all PE problems are existential; they will be outcompeted. What keeps a newly graduated Veterinarian from opening her own clinic and undercutting the PE competition? With no massive loans on her books, she can profitably offer lower prices than PE can. She may even drive the local PE clinic out of business.
First, opening a clinic requires some serious money. Then, if the new clinic gets traction, PE can make a very good offer for a buyout and the owner would have to be stupid or very stubborn to refuse. Most big companies these days just buy up competition. Good for the owners but bad for the customers.
How many veterinarians got into the game to become relentless, driven, scrappy and indomitable business owners vs because they love furry things and helping?