Not sure what your relevant experience is, but in my experience large healthcare institutions are constantly measuring their performance.

The problem is comparing it in a useful way across different institutions.

I have zero experience from the industry, but I still want to defend my point:

"Comparing it in a useful way across different institutions" seems like a BIG deal!

Institutions revealed to be inferior would have to improve close down. Those proven to do great work would be richly rewarded, but at all levels there'd be a new level of scrutiny.

This would be of huge benefit for patients, save tons of lives etc, but also put a lot of strain on doctors and hospitals, and I can see how people with power in those fields don't want this to happen and thus don't make it happen.

It's also entirely possible I babble too much about things I know nothing about here. If so, I'd appreciate learning about it!

Exactly this. My whole job is based on the torrent of data large healthcare institutions collect. The problem is not that people aren't writing things down - it's what to make of it.