Hmm. Making a universal email message have bespoke instructions for a specific mail provider. Call me old fashioned but I don't like that. Infact I still like to read my e-mails in plain text. Also, I dare say, not so useful for the many of us accessing gmail via Mac devices' mail clients.
Its all using open standard formats, and the specific schemas are open standards or proposed for standardization (and Google has said that its schema support may change if the schemas change in the standardization process.) Other providers could use it as well. This is how progress happens in open systems. The alternative is either abandoning the open system for new functionality, or just never getting new functionality at all. And its not the provider that is key here, but the client (the fact that for many gmail users the supplier of both the mail service and the mail client is the same makes it easy to confuse the issue.)
> Also, I dare say, not so useful for the many of us accessing gmail via Mac devices' mail clients.
Yes, features in the Gmail client that aren't included in other clients aren't useful to people using the other clients. I'm not sure why this is noteworthy.