> If they cost more AND they're less reliable, what exactly is the reason to not self host?

Shifting liability. You're paying someone else for it to be their problem, and if everyone does it, no one will take flak for continuing to do so. What is the average tenure of a CIO or decision maker electing to move to or remain at a cloud provider? This is why you get picked to talk on stage at cloud provider conferences.

(have been in the meetings where these decisions are made)