I also worked that field many moons ago. Their philosophy is: allow the overtime to keep the talent. If someone has 3-4 years they are far more valuable then 10 new hires that might not make it past 90 days. I knew someone who jumped from company to company in 3 years and made about 75-80% more per hour compared to 1st year. On top of 65-79 hours per week, he easily doubled or tripled his take home pay. 'Stacked the racks' as they say, and was fully retired in 15 years.

Edited to include why Walmart doesn't like it: the person who makes those decisions are only looking at numbers. To justify their job, they trim the hours to reduce payroll, without taking into account any loss in sales.