The other problem is that most of these things aren't easy to migrate to. AWS RDS is much easier because its just managed whatever you're already using. But cloudspanner? DynamoDB? You have to completely re-architect your application. Then you have to move your application, and data, to this new system...without massive outages. It's a lot of work and a lot of cost. So until things go HORRIBLY sideways, most companies don't have the spare time/money.
Been there, tried that.