But, for the system drive, the drive that's inside the machine where the OS is installed and loaded from, the drive that cannot be (easily) replaced on most Macs -- why, nowadays, would anyone buying a new computer they're going to use for several years want that drive to be an old-school, 200 MB/s HDD?

Apple still gives users the option to buy the slow system drive (i.e. shoot themselves in the foot) rather than forcing them to ante up for (at least a 256GB) flash system drive.

But, given it's Apple we're talking about, I find it really, really weird. Historically, Apple is notorious for denying the user these kinds of choices (e.g. a floppy disk drive, optical drive, user upgradeable RAM ...)

But slow system drives? Apple lets people buy those all day long. I don't get it.