Not everyone is you
A tablet is more than enough for 99% of people - these keyboards are a good input device.
Heck 99% of the time my laptop keyboard isn't used, because it's sat at work with a dekstop keyboard (and two monitors) plugged in. Ironically that means that the screen isn't used either.
My tablet on the other hand is pretty much alweays with me, and the keyboard is with me most of the time - when I want to write longer messages I open up the keyboard, easy.
Most of my tablet usage doesn't need the extra bulk. Emails/messages are relatviely short and the on screen keyboard is perfectly good enough for that.
Browsing requires minimal typing, again the on screen keyboard is fine.
I've not come across a laptop that boasts all day battery life, a mobile data connection, and fits in my pocket. The iPad mini2/3 does that easily - the keyboard can sit in another pocket, and I'm sorted.
Heck most of the time I don't even bring my "work" laptop to work (I'm permanently onsite and have a customer company laptop which tends to stay on site as well) because my iPad does everything I need (and more)