Some may have an availability dependency on those services, but if they don't have a full BC and DR plan ready to go within a few hours of losing those service they're not going to be a big enterprise for long.
Are you talking about a small WordPress site or something?
Very, very few tech companies could simply move everything to a new cloud provider in a few hours. I would even hazard a guess that almost none can.
I have all my infrastructure as code and can break it all down and spin it back up in kubernetes clusters in minutes. But due to the quirks of each cloud provider, there are tons of little fixes that would inevitably need to be made.
Not to mention that many companies have way more data than could even be copied over in a few hours.
The topic is having a single tech partner. If the partner is large enough you can have a high level of redundancy by utilizing their cross-zone/geographically distributed services (e.g. US East, EU West, Asia Pacific, etc).
How you got from "single tech partner" to "have no disaster recovery plan" I don't know.
