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."

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