I think in large part the average Walmart consumer does not shop like the average Amazon consumer. They load up a big cart over time rather than pull the trigger on lots of smaller, convenience-driven purchases. So Walmart is going to view a smaller cart size as a potential failure primarily because their operations are not optimized the same way that Amazon is.

It's a failure for e-commerce vendors because it's a spectacular success for shoppers, and the relationship between sellers and buyers is almost always adversarial.