Re: proving that....
As a senior IT bod at a major bank who publish research articles about cloud vs on prem that sometimes get quoted on theregister told me.
I've done work for many banks. I can tell you that the majority of them haven't had their own IT infrastructure for 20 years. Everything that can be outsourced, is outsourced. Only the very big guys do stuff on their own anymore.
For a large business, sure, having your own hardware makes sense. You are already going to be employing your own IT staff regardless of where the hardware sits, so you may as well put the machines in your own building.
However, far more businesses are of the smaller variety and it hasn't made sense to keep that stuff in house for a long time - even if you are a tech company. High availability for mission critical stuff is expensive, far more expensive than those Amazon bills. And, yes, I'm saying this as the owner of a tech business who hasn't had to deal with a server room for years.