Per Muggles:
I think some people are geared to naturally process multiple events at
the same time and do it w/o any issues at all. Then there are others
who can't walk and snap their fingers at the same time. The last group
of people shouldn't probably use a cell phone, talk to passengers, or
even play a radio while they drive.

Bingo!... I think we have an answer....
--
Pete Cresswell