No, not unless you are someone like Netflix. Usually you can configure multi-region failover and such and that will keep your things running. It is more expensive but for most use cases I think the cost is still less than the dev time/complexity of setting up multi-provider workflows and the inevitable duplication of resources (which is part of the cost of multi-region anyway)
No. And there's been a lot of talk recently about multi-provider being the right strategy to mitigate downtime, which IMHO is a farce peddled by expensive consultants. The parent comment is correct - this is why availability zones and regions have been established by each provider.
For the large majority of businesses investing in infrastructure-as-code far outweighs any crazy HA, redundant, multi-provider, whizzbang whatever setup you may have.
You can move 1.6TB between providers in a month for the same price as a single beefy DB server (m4.16xlarge here). That's a whole lot of logical replication..