Sure, but city life is neither for everyone. Of course you have a point if we were talking about a random
part of the Japanese culture - but is kohai - sempai not an important if not necessary part of Aikido culture? And therefore more a matter of proper education?
Well...that's the thing. It's an important part of Japanese culture, and it has correspondingly become a part of Aikido culture.
But that doesn't necessarily mean it's important any more than we should be eating Natto and drinking green tea just because Doshu does (I recommend both, but that's just my personal preference).
The question is, why is it necessary and what are the drawbacks? Especially, what are the drawbacks of implanting it in a foreign culture, and are the benefits really worth it?
IMO - the early instructors coming out of Japan (Tamura, Tada, Chiba, Yamada, Kanai, etc.) had gotten most of their actual teaching experience in university clubs during the build up after the war.
University clubs are notorious for their sempai-kohai shenanigans, and much of that was brought with them out of Japan.The sempai-kohai system was a familiar method for young instructors to impose order in a foreign environment. It might have been different if things had developed more organically.
I also wouldn't discount the effect of pre-war militarism on the martial arts - evidenced in the difference between koryu and gendai practices.