Shoppers cast shadows as they carry their bags along the waterfront in Portland, Maine, U.S, December 26, 2024. Kevin Lamarque | ReutersIt's not just Walmart.The leaders of companies that serve everyone from penny-pinching grocery shoppers to first-class travelers are seeing cracks in demand, a shift after resilient consumers propped up the U.S. economy for years despite prolonged inflation. On top of high interest rates and persistent inflation, CEOs are now grappling with how to handle new hurdles like on-again, off-again tariffs, mass government layoffs and worsening consumer sentiment.Across earnings calls...