The majority of men's suits are made in darker colors. Darker suits are more formal, and often easier to match shirts and ties with. Most businesses that still require suits and ties every day specifically require dark suits, while the offices that once saw lighter suits in daily use have gone to slacks-and-shirtsleeves dress codes as standards relax.
This leaves light suits as a predominantly casual wardrobe option — and a perennial favorite of sharp-dressed men who take advantage of the lighter shades’ rarities.
Light gray is the most versatile of all the light colors, and holds a special place in the wardrobe of any sophisticated suit-wearers.