[vr46]

Probably true, but my own experience tells me that they also run distinct services on multiple clouds that are unrelated and isolated, rather than running services across clouds. (For the most part: I have seen a few cross-cloud applications. Never optimal.)

[NewsAware]

If you have a company of 5k plus employees different teams are bound to use different cloud providers without even being aware of such. Such companies are also those being interviewed by Gartner or Forrester etc.

[Thorrez]

But since it's different teams using different providers, there's not much need to make a single diagram with multiple providers.