You can legally find out a considerable amount of information on someone with the info you would find on a job application (or in this case basic info on a medical form). Doctors are looking for people with large family that max's out their coverage every year and has no financial problems.
I was told by a friend, the ideal family is 2 well educated slightly over weight adults (over 40) with a family history of medical problems that are active or were active in sports and 4 school age children active in sports.
This type of family will probably have 10 or more doctor visits in a year. Twice yearly at least for the adults worried about their weight and health problems. Each child once for a sports physical and about two visits for an injury.
The worse a low income single male or a well educated working single mom with one child. I was surprised when she told me the later, but the explanation made sense to me. The doctor becomes an attention seeking means for the child and the well educated single mom is often overly concerned then demands seeing the doctor rather than a LPN. These type of moms often call several times trying to reschedule last minute to fit their schedule.
I do not know if what is or is not the ideal patient holds true for everyone, but I do know that doctors are concerned about bill collecting issues so some of the "better" doctors screen potential patients by self-publicated financial info (or public records) and stability.