Why? I type on an iPhone keyboard without any assistance as fast as on my keyboard. I'm almost touch typing. Even if you have to look at the phone's keyboard—you are way faster if the keys are at their expected place on the keyboard (which is QWERTY in my case).
Edit: If you disagree don't downvote, rather express why you disagree
I believe that my years of touch typing experience are the reason I hate typing on glass so much. I follow the text I'm writing and not the keys I'm pressing, so with no physical feedback about the locations of the keys, my text is an endless stream of aggravating typos requiring laborious correction.
I really miss my Blackberry. Every phone since has felt like the designers calculated the experience to be just one notch less annoying than the threshold at which I would actually pound the damn thing to bits with a sledgehammer.
Very different. Though I didn't realised how dissociated those could be before I used my Dvorak-like layout.