NEW YORK — After weeks of pushing early deals, retailers in the United States and some other countries tried to seduce customers with promises of bigger discounts on Black Friday, the sales event that still reigns as the unofficial kickoff of the holiday shopping season even if it’s lost some luster. Department stores, shopping malls and merchants — big and small — see the day after Thanksgiving as a way to energize shoppers and to get them into physical stores at a time when many gift-seekers do the bulk of their browsing and buying online. Enough traditionalists must still be around, because Black Friday remains the biggest day of the year for retail foot traffic in the U.S., according to retail technology company Sensormatic Solutions. “Black Friday is still an incredibly important day for retailers,” Grant Gustafson, head of retail consulting and analytics at Sensormatic, said.