A successful restaurateur I know used to say, "One lousy server can put me out of business in three years, one customer at a time." I'd guess that's about right.
You've met employees like these. They answer questions literally and provide no other information unless asked, are curt and surly and call it "efficiency". Their service isn't bad, but neither is it good. It isn't enough to complain about; neither is it worthy of recommendation. It can happen in any businesses, and it is deadly.
Recently I overspent $40 in a hardware store on stuff I didn't need, not because of bad advice from the clerk, but because of no advice. When I returned the product, she said, "I only gave you what you asked for." True, but a few questions on her part and I would have had the exact product I needed in the quantity I needed and I'd be a loyal and happy customer.
Instead I was embarrassed and unhappy. There's nothing really to complain about; it's clearly my own damned fault for asking for the wrong item. I still won't be back. She may be right, but I've got the money and with a little effort on her part more of it would be going from my wallet into her employer's cash register in the future. It won't be, but it could have been. It's called repeat business and it can bring future earnings to the skilled and enthusiastic worker.
Customers are notorious for not knowing the product and service nearly as well as they think they do. Customers routinely ask for what they think they want, which may not be what they actually need.
Customers are also free to shop or dine or stay wherever they will get friendly, knowledgeable, helpful and genuine sales and service. Unless they find it with us, they won't be back.