When Mary Hines joined Citigroup four and a half years ago, the ThankYou rewards program was not synonymous with Citi's brand — and it wasn't intended to ever be that way.

At its launch in 2004, ThankYou had its own separate identity, customer base and website from the rest of Citi – even logging into the program was difficult, said Hines, Citi's managing director of benefits, new product development and global rewards.

"It was supposed to be a coalition program that would serve multiple people," she said. "Sure, Citi would offer ThankYou points, but back then it would be offered across airline partners, supermarkets, department stores — and that strategy sort of came and went."

Banks and other businesses often try to blanket their customer bases with a loyalty program that follows the shopper from one destination to another, but in the U.S. the concept rarely works as well as a program that is laser-focused on one company's audience.

Indeed, Citi's ThankYou program flourished only after it pivoted away from the coalition model. ThankYou today is a proprietary program that rewards customers based on their interactions with other Citi products and services, like electronic funds transfers, direct deposits and online bill pay. Hines has helped oversee ThankYou's expansion across the U.S. and to nine global markets. Last month it launched in the United Arab Emirates.

Since just last year, the ThankYou program has grown 24% in number of redemptions and 8.2% in number of new redeemers.

"Rewards programs are even more important today than they were five years ago," Hines said. "Customer expectations have certainly increased, and the ability for customers to take advantage of them when you build the right experience really pays off."

Generally, the U.S. hasn't really grabbed on to the coalition model, said Sean McQuay, credit card expert at NerdWallet. U.S. consumers are programmed to expect rewards from their bank, but not from merchants and retailers. By contrast, coalition rewards schemes have been successful in European and South American countries, which also began offering credit cards much later than the U.S.

"Those banks have been offering these coalition programs basically from the very beginning since they were trained from the get-go that these coalition programs are the best way to go," McQuay said. "In the U.S. we've been trained for decades to just trust our banks to give us the best rewards. For the last few years as U.S. banks have tried to change that behavior with coalition programs, it's just failed to catch on."

Rewards are more commonplace than they were a decade ago, and consumers have come to expect offers and coupons and value them as though they were real currency, according to Michael Moeser, director of the payments practice at Javelin Strategy & Research.

But the coalition model is hard because, though it is marketed as being a more inclusive way to earn and spend rewards, it is limited by its inability to reach all of the stores that shoppers care about. For example, a user of American Express' Plenti program can earn and redeem points at ExxonMobil gas stations, but not Shell or Chevron because Plenti limits participation to one business in each vertical.

"Any time you can make the rewards currency more useable and relevant to the consumer, the more powerful it becomes," Moeser said. "The challenge we see with coalition programs … is that they may appeal to only selected customers who shop at certain merchants."

Hines said her team is working on that. It's embedding the use of points into third-party customer experiences like Amazon and the concert ticket merchant Live Nation; within users' online Citi card statement to cover charges; and in conjunction with Apple Pay transactions.

"When you load things into your [mobile] wallet, it just makes it easier to take advantage of the benefits of that card," said Hines. The friction caused by the transition to EMV-chip cards makes consumers want the simplicity of a mobile wallet, she said. "Experience is as important as what you're actually redeeming for."