Well, look at the picture of the green dress. It's a woman walking around somewhere outdoors, prob a park. So, that hints that the dress can be used for daytime walks and lunches. You wouldn't see a picture of someone in a Versace suit wrestling pigs around in the mud now would you?
Usually when it comes to promoting clothing, they use the background that is most fitting to the article of clothing. That doesn't mean it can't be used elsewhere though... that's up to the person.