I've never 'got'

But does your mobile really replace your laptop for internet access?
I don't have a laptop but if I did I doubt i'd want to trade a 15"ish screen and proper qwerty keyboard for pocketability.
Also when I'm not cycling I'm a biker so iv never been a satnav user.

Depends on what you do, doesn't it. Most sales people don't carry around 15" laptops anyway because they're too damn heavy and chew batteries too quickly.