Crooks use card skimmers to read the magnetic strip, then duplicate your credit card or sell the info.
“Crooks use card skimmers to read the magnetic strip, then duplicate your credit card or sell the info.”
They can’t duplicate the information which is on the chip that way, which is why “Chip and PIN” was introduced.
However, even in Canada it is generally possible to use a card only with swiping the mag stripe, even with a card that has the chip. Presumably this is so that one can still use the card that way in the event that the chip can’t be read.