The police can obtain records from the wireless carrier as to the activity at the time of the stop. If a text was sent, the time stamp would be incriminating. Cell phones are now routinely sent to a lab in traffic accidents where they are suspected of being the cause. I can't imagine anyone concentrating on texting while driving. Just a second or two with the eyes and mind away from the road can be quite hazardous.
Cell phones make for quite the PC buzz nowadays. But there are other distractions. I've seen drivers reading the paper while driving.
Mothers with heads turned while squawking at kids in the back set. Eating, searching for things on the floor, etc..
For those that golf, a great analogy for many of today's drivers would be a 30 handicapper playing from the black tees
Many drivers are handicapped enough without any additional distractions.