Than what do you save? Only the system-on-a-chip (CPU, GPU, RAM).
And the hardware to get an SoC with phone-like performance in a laptop or desktop form factor is relatively cheap, just because you have so much more space and power and cooling to work with.
(Your laptop-shell definitely needs its own power supply, whether that be a battery or a cable, because the screen alone will take more power than your phone's battery can provide for any sustained period of use.)
Right but if it's the same as a laptop why not just use a laptop?
The only things I can think of are you really want to keep all the data on your phone and don't want to use cloud sync solutions (Dropbox etc.), or you really want to save a couple of hundred dollars getting a (probably terrible) laptop without a motherboard. Not very compelling IMO.
Surely long term it'd be cost? A screen and a keyboard in a laptop shell should be a lot cheaper that a screen, a keyboard, RAM, SSD, fans etc in a laptop shell.
Those other parts of the laptop are cheap though. Sure not free, but chromebooks can be had new for just a few hundred $$$ (they don't need a fan either). If you want a fast laptop you need to spend a lot of money, but a fast laptop has the ability to have better RAM, SSDs and such than your phone because there is more space in that form factor and so if you want fast you are back to laptop while if you don't need fast your laptop is cheap.
