Let's see why celebrities like sunglasses.
First of all, they need sunglasses as shields from ultraviolet and protect their eyes and facial skin.Sunglasses prevent the eyes from direct exposure to the sun. This is also the basic use of sunglasses.
Second, they may don't actually like sunglasses, but they need them. As celebrities, they have less privacy. Every move of them are under focus. They need sunglasses to make themselves not that well-marked in private time.
Last bu not the least, celebrities are the fashion trend leader. They want to look cool and in, so they need sunglasses.
In comparison, glasses only help to correct vision problems. When they first come out, they have dull frames. When someone wear full frame glasses, other may think this person as nerd, geek or something.
Therefore, just you know why celebrities prefer sunglasses.