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)

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.