All of this presupposes that whatever you implement yourself will be more secure and/or that you have the budget to even begin to approach the same level of security.

I’ve been there, done that, and was amazed how the security aspects only rapidly escalated to many millions of dollars and an ongoing cost also in the million or two range!

Think of this like a CEO: they’re less worried about Chinese hackers and more worried about about insider attacks. They’re much more common and do way more financial damage.

The cloud automatically provides separation of roles because an entirely different vendor is in charge of the lower layers, such as networking and storage.

Do you have any idea how hard it is to prevent a smart sysadmin from simply copying all data to a USB drive and walking out of the building with it?

That’s much harder when everything is on a managed hosting platform and no single person can access all accounts / subscriptions.