Why can't you wear white socks in a suit?

Because business people usually wear dark suits if they want to look steady and dry. If you have a pair of white socks inside, it will look so dazzling and unsightly when you sit down. Now you pay attention to matching clothes, so what color is your clothes? Your socks should be the same color, and you must not let others see your legs leaking out after you sit down. That's why men's socks are so long now.

But it doesn't matter if you are casual.