We have multiple systems, some with a public API some not.
The biggest problem is simply support. We'd LOVE to have more public ability to interact but I simply can't support every independent developer out there.
Also, people agree to a legal terms of service to get access BUT don't always follow it (e.g., data storage agreements, use case agreements, etc).
Coming at it from Mazda's POV, it could be that but it also could very well be the monetization aspect.