Yes, we do... but you need to understand how the law works - the law punishes behavior, and (excepting DUI) the punishment is only after the harm has occurred.
What you're talking about is enforcing morality. Morality takes the stand that why is as important as what you do - problem with using morality as the law is you can't get people to stop lying about their motive. So we do the next best thing and punish the result of the behavior.
...not sure I really follow you here... ?
I'd think that texting while driving could quite well fall under (just thinking out loud) a distracted riving clause? Texting while driving is an action that's easy to prove (look at text message logs)
In my opinion, why someone texts while driving (to stick to that as one of the clearest examples of a distraction while driving) is irrelevant, it's the action of texting while driving that's important.