Don't confuse multitasking with motor skills.
Once you've learnt how to change gear on a car you don't need to give the task any attention. So anyone can stack lots of these automatic tasks like steering, switching on and off the turn signals, scanning for road signs, holding a legal speed, interacting with the other cars... breathing, blinking, moving the eyeballs etc. while actually using one's attention to talk with someone or philosophize about random crap.