It's not that one currency can rule all. It's like a government or a system. As I'm saying it is like a government in which the president is only the ruler. It needs officials such as vice president and secretaries to work. Just like bitcoin, it cannot run by bitcoin itself. It needs altcoins.
I agree and maybe bitcoin is the supreme to rule over all altcoins but still bitcoin need altcoins to make the cryptocurrency market run smoothly and become progressive.