Why do medical device companies recruit clinical practitioners?

Clinical practitioners are all practitioners! For example, you are a doctor in a hospital! There is a piece of equipment your hospital needs to purchase! They do! You're working part-time in their company, do you think it's possible? Take ten thousand steps back! You don’t have a job but you have a certificate! But if you have certificates, it means that your classmates or former colleagues are doctors, right? So it’s still reliable for you to sell this thing