Why? Time and I/O speed isn't as relevant for everyone as you might think. I sure don't want a system without flash memory, but I know not everybody is me and not everybody will care.

My mother bought a spinning rust iMac two years ago, sold to her as a "fast" machine. It was not fast. It took 15-30 seconds+ to do the most basic of tasks. It was unusable. I did what I could to remove background tasks and it was still painful to work on. She hated it.

I cloned the drive onto an external SSD with no other changes. Immediately she had a usable machine, and she now enjoys using it again.

Operating systems increasingly seem to be expecting an SSD. Windows is unreasonably slower on an HDD, extremely frustrating to use at all. IIRC that started with Win8, but might've been 10. Linux DEs, heading the same way. Wouldn't be surprised to find out that MacOS is like that these days, too.

That does mean OS/DE devs are hitting disk way the hell too often and just hoping modern disk speed makes it harder to notice, but there's no way that's not adding up to some real (but less crippling) latency even on SSD-equipped systems.

So it's not an option for you, me or your mom, but that doesn't mean it's not an option for the billions of other people in the world. (again, not saying it's a good idea considering the cost and storage requirements for a general user -- but again, not everyone is the same user)

Because it's really slow.

To us perhaps, but most western users are only a fraction of people on the world. Even if you take BRIC out of the picture you still have billions of people that either nave no computer or a computer that is so old a recent PC with a rotating disk is still way faster. It's very easy to get lost in a current context.

Sure, I'd rather have a computer with spinning rust than none at all, but we're talking about new $1000+ machines where there's no rationality behind using these disks in 2019, or even 2009. It's just a money making machine for Apple.