​Here's one place where paper still rules

Whatever Groupon's (GRPN) strengths, it may not be able to touch the enduring appeal of old-school paper coupons.

Americans can't kick the habit of clipping paper coupons from newspapers, fliers and mailings, according to a new survey from CreditCards.com, which found that 85 percent of consumers still use paper coupons. They're even popular with digital natives, given that 18- to 24-year-olds say they're about twice as likely to use paper coupons as online discount codes or other online coupons.

The results "show that plenty of us are still opening our snail mail and clipping coupons out of the Sunday paper like we have for decades," said Matt Schulz, CreditCards.com's senior industry analyst. "Americans are generally creatures of habit."

Unless it comes down to actually subscribing to the newspaper. While Americans still love their coupons, newspaper circulation fell in 2014, hitting both weekday and Sunday editions. Still, many consumers go out to buy the Sunday paper simply for the coupons, Schulz noted.

Still, Schulz said he was surprised by the survey's results, considering it was designed to find out how many consumers use the opt-in deals credit cards offer. These deals provide discounts for consumers when they buy items with their cards, such as ordering flowers from a floral service.

"What we found is about half of American credit-card holders don't realize that these card-linked offers are out there," he said.

Other digital coupons didn't measure up to paper, either. The study found only 17 percent of consumers enter a discount code on a website, and 15 percent use smartphone coupons or discounts.