Suddenly? Nothing sudden about it been going around for years.

As for why it's because it's super easy and if someone gets one of your checks they have your full routing and account number on the bottom which can be easily used to make a fake one or initiate an ach or something. Since its old technology that for some reason banks refuse to update, you get a credit in your account within a few days of deposit while the actual account holder has time to notice they've been robbed or their bank has time to catch any obvious fake checks. In the meantime the fraudster is already free and clear with however many giftcards they got.

Checks are still commonly used for businesses and people working predominantly blue-collar professions (at least in the US)

Surprised that cheques are still a thing.

The banks here made old fashioned hold-outs like me give up our cheque books about 10 years ago.