It's not hard to understand, even though it's completely insane. People simply don't think about driving as a dangerous activity requiring their full attention.
This is actually one of my favorite things about riding a motorcycle. It removes the 'safety net' of the car and forces one to pay full attention to the road. Texting is simply out of the question.
Unfortunately it is also one of the least favourite things about riding a motorcycle - always having to look out for car drivers who are not paying full attention to the road.
Well of course there are exceptions. Personally I've tried the "emailing from my laptop while riding a bicycle" thing - you take your hands off the handlebars, swing your backpack around (that's the hardest part and most likely to bring you of-balance), take out your laptop, open it, wait for it to come out of sleep and compose and email with one hand while holding it with the other. Of course on an empty park path with a friend to watch out for other people. Depending on the inherent stability of the given bike frame, and the weight of the laptop, it's actually not that hard...