Dresses are meant to be worn on the shoulder and off the shoulder is a dress style that breaks this rule. These dresses are trending right now because they show some skin and can look sexy. Many people believe that this is a trend because of the way society has gotten more open with sex, but it's possible that fashion trends are cyclical and this one was just waiting for an excuse to come back.
Some ladies feel like their shoulders are big and that it looks funny when they wear the (not over the shoulder) look because it makes them look bigger than they are.
This is a trend that was popular in the 1980's and 1990's because shoulder pads were all the rage, but it also looks good now because of all the shoulder and neck scarves that have been popular in this decade.
There are many different designs, styles and colors of off the shoulder dresses available. They are made to fit any body type. If you don't like how it looks on you, there is one for you somewhere. There is no set way to wear one of these dresses because it all depends on what type of shirt or top you want to wear with it. You can wear off the shoulder dresses with sweat shirts, short sleeve button up shirts or button down blouses.