Neither does a cell phone, but that doesn't stop people from carrying one 24/7 everywhere they go.
One other reason to have a Passport for going to Canada. A couple of years ago, I was caught going 34 in a 20 zone. Because it was a school zone, there was a mandatory court appearence. The drivers' license is taken as bond, your citation becomes your temporary drivers license. Before the court date, my father-in-law died in Canada, and I had to go to the funeral. I would have had a fun time trying to explain a speeding citation as a driver's license to the customs folks in Edmonton.