Unfortunately, a yearly tax has a margin, so the vendors have been dragging their feet. DigiCert and GoDaddy have bribed the Azure team with kickbacks and wholesale discounts, so Azure is now refusing to implement anything else. Why would they? They get a margin on every issued certificate!
So please: If you have a presence in AWS or Azure, call your sales representative and pressure them. Submit requests through the feedback portal, and vote up existing requests.
Raise this regularly, or it will never happen by itself. The incentives just aren't there!
Pressure must be applied by a large fraction of the customers.
You are that customer.
Apply pressure.