Comment by rcxdude

I think it's more a degree of how much effort it is to adjust to the new interface. If it's just 'added a new parameter to a function and there's an obvious default for existing code', then it'll (potentially mechanically) be applied to all the users. If it's 'completely changed around the abstraction and you need to think carefully about how to port your driver to the new interface', then that's something where there needs to be at least some longer-term migration plan, if only because there's not likely one person who can actually understand all the driver code and make the change.

(I do have experience with this causing regressions: someone updates a set of drivers to a new API, and because of the differences and lack of a good way to test, breaks some detail of the driver)