Why can we only ban one champion?

If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up If I ban Zed, Yasuo shows up If I ban Yasuo, LeBlanc shows up If I ban LeBlanc, Fizz shows up If I ban Fizz, Yone shows up If I ban Yone, Zed shows up