You're kinda missing the point here.

Yes, mobile phones use touchscreens, and billions of people have smartphones, that is correct. Yes the audience of HN is far removed, not gonna argue that. Because that's not what we're talking about.

Grandparent very correctly points out that mobile phones haven't replaced traditional keyboards, in fact there's probably more keyboards being sold now than at any point in history before, that's because phone touchscreen haven't replaced keyboards, they're just a new interface for a new device. 15 years later other devices are still using other interfaces, and the actual places where it has been replaced are not that many. Only point of sale machines and cars come to mind having replaced keyboards (and I'm being very generous, honestly I wouldn't even call that keyboards) with touchscreens, and some car brands are even starting to walk it back.