It would be super useful to have an API which identifies what type of controller someone is using.
This would allow us to create button prompts for a variety of controllers.
It is important to note that different controllers have different types of vibration motors inside of them, and thus applying the same amount to each can result in different experiences.
Other types of controllers like VR controllers can be extremely different. Vive and Oculus controllers are completely different mappings from one another. This makes it difficult to create games that support both.
I could go on, but I think you get the idea. Not all controllers are the same and as such, they probably should not be treated the same.