Why not run Apple's latest? Because it in no way furthers computer science. Because it has no breakthrough technologies that benefit all. All that's found there are technologies that benefit Apple - and detriment the consumer. Apple has grown from a lucrative beige box startup into a trillion-dollar monster whose sole goal is total control. Apple wants total control of all commerce on all Apple computers. Their harsh 30% cut, three times the industry norm, and expressed only indirectly, never as '30%' but only as 'you the software vendor get to keep 70% of your own revenues', is perhaps not the ultimate issue. That issue can perhaps be that Apple - and only Apple - gets to decide what is run and what is seen on computers they sell. That Apple would prefer that all third-party software have the same 'look and feel' as their own software is understandable, if not completely justifiable - after all, the choice of what runs on the consumer's own property should be up to the consumer and no one else.
But Apple goes further than the above. Apple blocks any third-party software that makes them look bad, that, directly or not, reveals cracks or discrepancies in their own products and in what they have been telling their consumers.
Utilities that work at a system level deeper than standard application software will be blocked. Utilities that show consumers how Apple has been lying to them will be blocked. And so forth.
But ultimately it's back to the money angle again, for it's now estimated that, by controlling the flow of software to consumers, Apple brings in additional revenues of between 60 and 80 billion dollars per annum, and all that software has done is reside on Apple's storage disks. That is a staggering sum. It is unprecedented in any industry, and has met with condemnation by Forbes magazine, Fortune magazine, and The New York Times, amongst other publications.