[politician]

Cloud vendor feature signaling, mostly.

Microsoft wants you to use CNTK on Azure. Amazon wants you to use Mxnet on AWS. Google wants you to use Tensorflow on GCP.

It's irrelevant whether these frameworks can be used outside their home platform by broke college students. That's a red herring. The cloud vendors are looking to sell enterprise contracts, and they need to check all of the boxes.

This strategy makes complete sense from a business perspective, and you really cannot fault them for doing it.