[Qwertious]

>It can be held in hands and used.

So can a 15" laptop. That doesn't make 15" laptops handhelds.

[Tyrannosaur]

If by "held in hands" you actually mean "sit on top of your lap" then you may understand why laptops aren't called handhelds.

[neoberg]

I really want to see how you can hold your 15" laptop and play a game or type something while doing that.

[Qwertious]

Put the palm of your off-hand at the centre underneath the laptop, put your main hand on the trackpad.