“Bonjour” “Good day” “Góðan dag”
French, English or Icelandic, no matter the language, it is expected that when a shopper enters a store in Europe they will greet the shopkeeper. And of course, the shopkeeper will respond in kind.
The reason for this is a matter of perspective. In the United States, customers view stores as a public place. But in Europe, stores are viewed as private property. Just as you would never enter someone else’s private home without greeting them, you would likewise never enter a “private” store without a greeting.