When you're a working adult, doctor's notes become a thing of the past. When you must miss work to go to the doctor, you usually tell your boss, and they believe you. I understand why K-12 schools might want a student's doctor's note to prevent truancy, but they are still a bit of a hassle, especially when your kid is already sick.
One woman recently got into an unusual situation where her boss asked for a doctor's note from her wife's doctor. She decided to take four days of paid time off to take care of her wife after she had an operation. She got said time-off approved three months in advance. Two weeks before the surgery, her boss asked her to get detailed proof of her wife's surgery to explain her absence from work. All in all, this is a super bizarre situation that neither of these women deserve.