Because of momentum and backward compatibility. What you say may make sense from a purely technical point of view, but you are not considering that 99.999% of I

Because of momentum and backward compatibility. What you say may make sense from a purely technical point of view, but you are not considering that 99.999% of Internet users are average users. Without backward compatibility you have no way of winning. And with backward compatibility you have... the current mess of patches upon patches.