[int_19h]

New features in the API indirectly benefit the end users (once apps start using them). But those new features don't have to be breaking, and that part doesn't help the users at all. It does help Apple spend less resources on maintenance, though.

[newtritious]

Changes to old features also benefit the end users, and they do have to be breaking in a significant number of cases.

If you think there are no insecure or inefficient APIs in older versions of operating systems, then you are simply wrong.