With a few exceptions for companies with highly secretive data, you do have to be a government agency or working in a highly regulated government-adjacent area for secured private clouds to be a requirement carved in stone and therefore worth investing a ton of extra money into though.

Just off the top of my head: Healthcare. Banking.

Neither approaches the secrecy needed by government installations. Health care and banking leak PII regularly and never really suffer any consequences.

This is just inaccurate

Anecdotes are not data.

Healthcare and banking have no issue storing data in third party datacenters as long as they meet the applicable standards.

You absolutely don't need this or FedRAMP to do healthcare.

i'll add that on-prem is getting 10-100x easier than it was 10-20 years ago (still very hard), and "i want to run this in my own datacenter" is becoming accessible to much smaller companies than just F500 enterprises

Huh? 20 years ago on-prem was the norm and the cloud didn’t exist.

Yeah, AWS was in private beta in 2005 and public in 2006. People knew it existed but didn't have access yet. https://www.zdnet.com/article/how-amazon-exposed-its-guts-th...