Earlier quoted context omitted.
As programmers, the bus factor is something to be noted and avoided, but in medicine, it goes the other direction. Private practice is one doctor, and a whole support staff for that single individual. Why are we so eager to be replaceable?
Doctors keep patient notes, and EHRs and patients can recall histories separately to that doctor. Doctors also go through relatively standardised training. That single individual is important, but it's not the same. What's more the same would be if they were practicing healthcare on a species that they had invented, and no one knew anything about it, and the species was crucial to a company's survival.
Aka, why we should ask vendors for their source code in case they go under.