For many big box retailers, it's purely a numbers game. How many people get superior customer service at Wal-Mart?
It's more of a puzzle in the jewelry business, but maybe not so. Big box jewelers don't necessarily attract the best salespeople, and their pricing is such that people buy from them regardless of the quality of service. B&M guild jewelers only shoot themselves in the foot when they provide poor service. They don't have the advantage of numbers that the big box stores have.
I remember in a past life being taught the rule of 25. Upset one customer, and 25 other people will know about it either directly or indirectly. Same for making one customer happy.