How do you treat your guests? You probably want to make them feel at home. 
You offer them the most comfortable chair; you serve delicious food; you're attentive to their needs for snacks and drinks. That's hospitality, and when someone visits your home, they are grateful for it. A guest does not pay for that hospitality.
When I enter a store, however, I do not consider myself a guest. While I expect that the store will be clean, well-stocked, organized and brightly lit, I don't expect that store employees will offer me a recliner and a cup of tea, take my shopping list, and return ten minutes later with my loaded cart. That's not how stores work--although it might be really nice.
People who buy things in stores are called customers. Certainly they should be treated courteously by the employees in the store--and when they complete their purchase, they should be thanked. Customers keep stores in business. Guests do not. They're just there to visit, not to spend money.
Note that I am not speaking here of the hospitality industry; what I'm protesting is the use of the term "guest" to describe someone who enters a fast-food restaurant or discount store with the intent to purchase goods and spend money. If a retail establishment wishes to keep me as its customer, it'll treat me like a customer. I used to work in a bakery, and we were taught to treat customers well. First we would greet them; we'd take their order and pack it up, remembering to ask if they would like something else. Finally, after they paid, we would thank them for their purchase.
That's back when customers were customers. Since customers have become guests, when's the last time you were thanked for your purchase?
Maybe that's one reason I prefer to shop online. And with coupon sites like Ultimate Coupons or our sister site Tjoos to bring us all the best deals, who needs brick-and-mortar stores anyway?
