If you compare to most if not all European airlines, you could say that North American airlines also have a dual system but actually it's a little different to LY's system. With NA airlines, you do not get lounge access without club membership (even if flying First) except in some cases when traveling internationally. For this reason I see it differently from LY. LY has overlap between KD and Matmid in lounge access, business class check in, priority baggage handling, and I believe priority boarding. That's why I call it a dual system and think maybe they are simply planning to abolish that.