Recently, it has not only become difficult to get a quota in some regions, but even if you have one, it doesn't mean that there are available VMs. Even if you have a quota, you may need to move your bundles to a different subscription when different VMs are available. That's why flexible node types can help, as databricks will try to deploy the most similar VM available.

Watch also in weekly news https://www.youtube.com/watch?v=sX1MXPmlKEY&t=672s