As an apple alumnus, I believe it has to do with a culture of "laser focus"
There is an internal course called "what makes apple apple" that you can take, but it's not necessary to pick up one of the key pieces of culture: the importance of saying No to most things.
Apple has built their reputation on high quality. To continue to deliver takes immense effort, even for incremental programs, and often almost if the talent internally shifts to whatever is new or deemed important, at the expense of everything else.
So it's not that they don't know, it's not that they don't care. It's that they believe in sacrificing opportunities elsewhere so that they can focus on what is truly important.
Another shift that happens internally is executive focus. Executives at apple are extremely hands on with products. They don't micromanage, but instead constantly judge whether a product is on course and has taste. We use to prepare monthly keynotes that went all the way to the top, hitting each executive along the way, who was interested in taking the pulse of every project underneath them. This approach does not scale to more than a handful of product lines per executive.
There is a lot of risk inherent in this approach, because if they line up a home run with half the company over a few years and then you whiff, you could be in a tough spot. By that's exactly what apple does. And one of the advantages is that people are rarely worried about whether apple is committed to an entirely new product, because they go all in each time they move. For example, apple is absolutely committed to making the watch dominate the smartwatch market. It isn't a hobby for them.
The solution the internal apple devoutiees would see to this problem is to cut the Mac mini entirely if it stopped selling, rather than refresh it. It is believed to not be worth splitting the companies attention.
Edit: as other commenters have mentioned, apple is also not the largest maker of these products, just the one with the largest valuation. They have less, more focused talent, and larger margins.
Edit edit: I just remembered the giant picture of Steve jobs in Infinite loop I used to walk past to lunch all the time that said "I think if you do something and it turns out pretty good, then you should go do something else wonderful, not dwell on it for too long. Just figure out what's next." pretty much sums this up.