Say you own a small market and a WalMart opens up across the street with a wider selection and cheaper prices, it's going to be bad for your store. People still might come to your store. Maybe you sell one or two special items that WalMart doesn't carry. But if they have lower prices and a wider selection most people are going to buy most of their stuff from the WalMart.
I'm basically the bedraggled old lady who's been shopping here for years. I'm friends with the cashiers and enjoy making small talk with the other shoppers. I think WalMart is shit because everyone i'm used to making smalltalk with is over shopping at WalMart now.