Short answer is because there are so many different type of occasions.
Among different types of suits that are worn today the first is the dinner suit. It is part of a black tie suit which arose as a lounging alternative to dress coats in much the same way as the day lounge suit.
The second type of mens suits is business suits. A business suit is a lounge suit mostly preferred by businessmen. It is most suitable attire for men while going for conference, conducting meeting or any other business activity. There is a range of choices available in business suits in different style, color and fabric.
The next type is wedding suits. Wedding suits are worn on special occasion like ceremony, marriage party etc. and displays esteem on special occasion. These suits are fusion of rare fabrics and classic style with an elegant touch. Another type is designer suits. Designer suits are one of most favorable choices of everybody. As fashion changes, these suits also changes from year to year and sometimes can be tricky to buy. These suits can be found in many different styles, materials and colors.
There are also vintage suits. Vintage suits usually consist of 3 pieces: the trousers, jacket, and vest. They can be found in many different colors and patterns, but will traditionally be made up of the same 2 materials that is wool or polyester. The list of mens suits is endless and it goes on and on like there are church suits, dress suits, classic suits, Italian suits and contemporary suits. In the market, mens suits are available for every occasion.
So, there you have it.