There's zero business case because they want to sell you a laptop and subscription to iCloud.
Improving FreeBSD will make it easier to run BSD on non-apple hardware which will eat into their bottom line.
The number of people who will buy a Mac to run BSD is a rounding error, and those people won't buy iCloud subscriptions anyway.
> Improving FreeBSD will make it easier to run BSD on non-apple hardware which will eat into their bottom line.
The number of people who want to run FreeBSD on their laptops probably numbers in the hundreds. Not exactly a threat to Apple's bottom line.
On the other hand, some of those people are FreeBSD developers who create and maintain code that Apple would like to have the option of using. That relationship is worth something to Apple.