The more I think about it, the more I would agree for a single reason: Costco is exponentially busier than other stores.
I can't remember the last time I couldn't find a parking spot at a "big box" store.
I can certainly remember the last time I couldn't find a spot at a Costco: Basically every weekend.
But if you take let's say 8PM on a Tuesday at Costco, their lot is quite devoid of carts, just like your regular big box store.
2PM on a Saturday? Tons of carts everywhere because there's tons of people.
I've seen Walmart in a disaster state during busy shopping holidays.
So I'm fairly certain it has much more to do with volume of customers rather than the brand of store.