Different use cases: somebody may want a portable workstation, not a tablet with keyboard.

I am typing this on one: it's still technically a laptop, and I can still unplug it from the plethora of peripherals and take it for a walk - it's just that I rarely do that. Still, it does happen every month or so, so there's some value in the laptop factor. (Haven't moved my desktop computer for years, am using both; and on the road, the smartphone is powerful enough.)