Not every doctor also wants to be a small business owner. Usually what happens is a doctor/dentist/vet started a practice, wants to retire, and sells it to PE.

Not every doctor also wants to be a small business owner. Usually what happens is a doctor/dentist/vet started a practice, wants to retire, and sells it to PE. At smaller places, sometimes the owner sells to PE and stays on - they just don't want to deal with the business side of things anymore. Quitting your job to start your own thing is never an easy step.