I thought the whole promise of electronic records was to avoid transcription errors -- if the doctor enters it into the record himself, there's less chance of someone misreading or mistyping his notes later.
If I were given one guess, it would be that the medical purpose for authentication is to avoid accidentally corrupting the data, e.g., typing Alice's prescription into Bob's screen. But the authentication technology is distorted by a security purpose that may be unnecessary and is being regularly bypassed.
For instance, just having people enter their initials into every entry or screen would go a long way towards eliminating erroneous entry, without being too burdensome.
This IS the selling point, therefore we can catch all errors!
WARNING: patient medication dose higher than expected (override)
WARNING: patient already received dose within recommendations (override)
WARNING: patient is allergic to medication (override, mistake)
Reality on the ground is that there were governmental subsidies to implement them, so everyone got them.
How much they actually help vs create problems is still an open research problem