Because they can. Vintage Champagnes are made mainly from the best grapes from the choicest vineyards. The extra aging adds more complexity to the flavor and gives it needed maturity. Non-vintage champagnes are sometimes too young to drink when they are released. Vintage Champagnes use the grapes from one year only-an above average year at the least, a superb year at best.
Champagne ages faster in warm temperatures.
They don't tell you that Champagne almost always improves with some aging. Prolonged, excessively cold temperatures numb and flatten the delicate aromas and flavors of Champagne. Also, the odors of various foods in the fridge can eventually penetrate into the Champagne. And the vibrations from your refrigerator motor are not good for Champagne, either. Yes, they certainly do.