Seems like an easy question but since SQL MI already requires a subnet delegated to it, Why Would you use a private endpoint? You already have a private IP address which will keep traffic contained to the Azure backbone? In my case we have a DB used for analytics and we are migrating it to SQL MI since x-db queries and linked servers are used. Seems like a waste of a subnet to create one only to host the private IP and NIC. Something I'm missing here? An answer would be greatly appreciated.
A private endpoint is not required to run SQL MI but can be used to accelerate access. The feature is still under review.
Here is a link to the documentation on private link and sql mi. link italic bold
The PE use is related to the Connection Type option taken when configuring SQL MI.