It's not always a full availability zone going down that is the problem. Also, despite the "no one ever got fired for buying Microsoft" logic, in practice I've never actually found stakeholders to be reassured by "its AWS and everyone is affected" when things are down. People want things back up and they want some informed answers about when that might happen, not "ehh its AWS, out of our control".

When there's little trust between the business and IT, both are incentivized to move to the cloud.

It's harder to build trust than the opposite.

OTOH, when your company's web site is down you can do something about it. When the CEO asks about it, you can explain why its offline and more importantly what is being done to bring it back.

The equivalent situation for those who took a cloud based approach is often... ¯\_(ツ)_/¯