alt Hacker Newsbecause phones are not general computing devices, and really shouldn't be. They are too important to modern society to be unlocked for their full potential.
That said, I doubt the average person on a laptop even needs a general computing device, so your point does make sense. Though, is carrying around a screen and a keyboard and cable any better than carrying a laptop?
I could see an argument of it being cheaper, but that would take years, possibly decades, of multiple competitors in the space for the market to make that true.
Now, if we could have a decent folding keyboard and monitor that fit into the same case as your phone, that would be a game changer, but I don't think anyone is risking the investment to develop that.
People want a full-size keyboard. Adding a couple of millimetres underneath that keyboard allows you to put a whole computer in there.
We have laptops because it makes sense. Look at Apple's Macbook Neo. The tiny logic board on that computer is the least of Apple's worries. The most expensive components are the display and case. Why not charge 100 bucks more and not have to worry about this thing being a phone accessory?