Plus and cons - computer / tablet :

Tablet: (Android or Ipads)
 +flat rectangular format, handy to carry around or use anywhere anytime
 +touch screen, draw onscreen or modif pictures easily
 +reading books or docs/comics on the tablet is very good (touchscreen and apps..)
 +integrated GPS and sensors like phone
 +integrated dual camera
 + OTG enables all USB devices/support (Android only ?)
 + 2G to 5G SIM support like a phone (Android only ?)
 + zooming for anything when surfing/reading/photo or 
for toying/drawing (zoom with 2 fingers) makes it very 
good in many situations.
 -can't boot on USB or SD card
 -can't replace the system usually (risk bricking the device / not supported)
 -only 1 USB plug
 -no HDMI or other plugs (thought supported on the USBtypeC or WiFI)

Laptop: (Windows/Linux ..or eventually Mac or ChromeOS)
 +integrated keyboard/mouse (easy text writing and mouse desktop app activity or FPS/click gaming)
 +can boot on USB and able to entirely replace OS with anything available for it
 +many USB (sometimes not so much tho)
 +other plugs HDMI etc (not all the time)
 +ability to change internal components (not all the time), add memory change hard drive ssd
 +can emulate an android system to run android app cause the other way around is no usualy (a tablet emulating a PC only works for old systems)
 -no touchscreen usualy
 -reading books or docs/comics on the laptop is less confortable (needs key scroll or mouse etc)
 -less handy to use thought still very portable sometimes (reading news is better with a tablet in a sofa/bed or in a transport)
 -no GPS, no sensors
 -camera more limited and only 1
 -no 2G..5G SIM
 -zooming needs a special app and is not well integrated / unhandy. 
 ---> new laptops may have less USB plugs (type C), components might be soldered (netbook like)
        laptop may not be easily dismountable to change the battery (risk breaking it when dismounting/declipsing it)

note that there are computer tablets (tablet running Windows instead of Android),
which is a mix in between that could run android apps via emulation, have 2 finger zoom, or other tablet things, but it may not be able to boot via the USB plug and it looses the other '+' of the laptop, but may not get all the '+' of the tablet: may not have GPS or other things.

Now...if you take a tablet and a support or a flipcover support and bind a bluetooth
USB mouse and keyboard you have exactly the same as the laptop but with the OS
of the tablet.  And most Apps with will have their equivalent or even more up to date
ones because of all the active development for the mobile OSes rather than
PC.

Techies: Android tablets run on linux  internaly and can also run a complete linux environment
including linux distribution graphic/sound apps using termux 
(not emulated but compiled for the architecture of the device) - virtual root linux.
it is possible to build programs for Android itself right on the tablet with AIDE even in
native app mode, also with gcc on virtual proot. And OTG enables Arduino programming
also. (3D acceleration is not available on virtual proot linux/termux)

conclusion:
laptops or other computers have already reduced and will
probably disappear in the larger scope of the average
people in favor of smartphone of course or tablets.
User have a laptop but instead he uses his phone or tablet,
and only use the laptop for specific tasks. All other things
related to online stuff or photos/toying/social net or gaming
and/or a console dedicated to gaming.
means that the laptop would get dusty enough.
also the fact that there is much activity around the mobile
dev/appstores and easy direct  access, while the computer
side would look a bit more boring and unfriendly.
Note also that printers especially but other devices are
now compatible with mobiles (smartphones and tablets)
which means that someone with a high end phone 
(or normal phone/tablet also ofc) will
gladly directly print from his phone, rather than starting
a computer.

then many computer users were not interested at all into
changing the operating system of their devices which
makes the '+' about USB boot and OS change not very
important for many.

the PC gamers are still active, with steams or other PC games (maybe compatible with xbox store), not sure
if it will remain the case in the comming years, many
exclusivity on consoles only, and more adapted game
experience on console, that is the game will run how it
is supposed to run on the console, you don't have to change
your graphic card or do adjustment etc, however PC side
still has all pirated games, but the pirated version usually
don't work online.