It doesn't really matter if it's public or not. The fact is people are using those APIs and there's nothing that can be done about that. Nonchalantly breaking stuff and rejecting applications actively subtracts from the value of their platforms and could alienate developers.
Microsoft had private APIs and data structures too and it didn't stop developers from using them. However, their approach to that was different: they maintained bug compatibility with old software in order to keep stuff working. This is one of the main reasons why Windows remained relevant for so long.
The fact is Apple simply doesn't care about backwards compatibility. It's not just private APIs, public ones are also at risk:
> A lot of developers and engineers don’t agree with this way of working. If the application did something bad, or relied on some undocumented behavior, they think, it should just break when the OS gets upgraded.
> The developers of the Macintosh OS at Apple have always been in this camp. It’s why so few applications from the early days of the Macintosh still work.
> For example, a lot of developers used to try to make their Macintosh applications run faster by copying pointers out of the jump table and calling them directly instead of using the interrupt feature of the processor like they were supposed to.
> Even though somewhere in Inside Macintosh, Apple’s official Bible of Macintosh programming, there was a tech note saying “you can’t do this,” they did it, and it worked, and their programs ran faster... until the next version of the OS came out and they didn’t run at all.
Microsoft had private APIs and data structures too and it didn't stop developers from using them. However, their approach to that was different: they maintained bug compatibility with old software in order to keep stuff working. This is one of the main reasons why Windows remained relevant for so long.
The fact is Apple simply doesn't care about backwards compatibility. It's not just private APIs, public ones are also at risk:
https://lists.apple.com/archives/cocoa-dev/2019/Oct/msg00004...
It's not a new attitude either. Apple has always been like this:
https://www.joelonsoftware.com/2004/06/13/how-microsoft-lost...
> A lot of developers and engineers don’t agree with this way of working. If the application did something bad, or relied on some undocumented behavior, they think, it should just break when the OS gets upgraded.
> The developers of the Macintosh OS at Apple have always been in this camp. It’s why so few applications from the early days of the Macintosh still work.
> For example, a lot of developers used to try to make their Macintosh applications run faster by copying pointers out of the jump table and calling them directly instead of using the interrupt feature of the processor like they were supposed to.
> Even though somewhere in Inside Macintosh, Apple’s official Bible of Macintosh programming, there was a tech note saying “you can’t do this,” they did it, and it worked, and their programs ran faster... until the next version of the OS came out and they didn’t run at all.