Why  15.6 inches screen size?

 The main reason I believe is  that for people or consumers or  senior  citizens  who

 want only one computing device , 15.6-inches screen size hits the sweet spot.  Take for example ,  a   Laptop/Tablet/Smartphone(ALL-in-ONE)  machine which I mentioned earlier that has  a screen size of  15.6 inches and with that  15.6 inches form factor , it is the minimum screen size to achieve the kind of usability , required in having only one device , required in having only one computer ,  required in having only one machine , which they can use as a 5G Laptop , which they can use

as a 5G Tablet  and BEST OF ALL which they can use as a

5G Smartphone .......a  big 5G smartphone ....... a  big 5G smartphone has a screen size  of    15.6 inches .