Andy Puzder may have stepped down as CEO of CKE Restaurants, but he still has a finger on the pulse of the restaurant industry. “Really, if I were staying on as CEO at CKE, I think my biggest challenge would be to determine how you adjust to the different way people are purchasing things,” Puzder said Tuesday on CNBC”s “Squawk Box.” Puzder, whose last day as CEO was Monday, said shifts in how millennials purchase everything from clothing to groceries has reached restaurants. Chains like Panera and Starbucks have incorporated mobile order and pay options, while McDonald’s now has digital kiosks. Of course, these digital innovations haven’t come without growing pains for companies. Starbucks, which has seen great success with its mobile order and pay app, reported in Januarythat an increase in digital orders actually hurt its same-store sales. Congestion at the hand-off counter caused incoming customers to leave without making a purchase, despite lines at the register being short, Kevin Johnson, Starbucks’ president, and soon-to-be CEO, said at the time.