Sure, and the next would be stopping from breathing and blinking eyelids and growing hair.
Sorry, many of us can multitask, ...breath, swallow, smell, sweat, SEE,HEAR, phart, burp, hiccup, and envision the destination, see the map in their head, street name, city name, see the speed signs and adjust speed to be correct, see stop signs or lights and react....& MUCH MORE.
Talking is a minor thought process as you do not have to face the person you are talking to...so there are no secrets in a bus. A cell phone is totally different as the person at the other end asks specific questions you have to think about that is not ROAD RELATED. SOMEHOW IT IS DIFFERENT. Some people CHOOSE NOT TO TALK, others sing, and play air guitar or air drums. Those who do, do. Those that don't, don't. It is the choice of the driver. Fortunately, there will be auto drive cars in the near future.