To sell more hardware?
Obviously I get your point, but there's a bunch of customers who would like good ARM hardware but can't accomplish their work with macOS. It's not like Apple needs this tiny market, but it wouldn't hurt them either.
Citation needed.
In the x86 sphere it isn't that much better either, most ACPI tables are thoroughly broken if Linux announces itself as Linux and not as Windows. In fact, a lot of machines' ACPI tables barely work on Windows.