LOL, yes, and even people not all that young. I carry my phone, which has a case with slots for cards, and my driver's licence and debit card, plus health card, are in the slots. I have one of those metal credit card cases that I keep in the vehicle, with the point cards from Shoppers, Loblaws etc., but I leave my credit card at home. I have cash in my pockets or some in the phone case; if I have to carry a bunch of stuff and need my tablet, or perhaps a notebook and writing utensils etc., I have a bag very similar to the one pictured in DM's Yukon, with a zippered top and a shoulder strap. I like that's it's washable because i have been known to spill beverages or dog treats in it.
I was surprised at how many cards DM had in the Yukon but not by the fact that he had them. If they were in his pocket in some wallet when the crime was committed it would stand to reason he took them out and maybe rinsed them off, who knows.