It's one of those Japanese-specific cultural things that must not be considered at value face (the "official explanation"). Not the meaning and reason why they do it but the actual social implications.

I personally think chat rooms are awesome and I miss the golden days of mIRC. But air replies don't work like a chatroom and are not the same. As much as they can be rationalized as politeness and consciousness, they can also be extremely alienating.

Japanese people definitely do not engage in the same (level of) passive-aggressive subtweeting we see in the West, that's true. But for instance, to me all air replies do is pollute my feed with incoherent half conversations because I don't follow everyone - and I don't want to follow everyone.

It's like the Japanese culture of wearing masks. Officially, a sign of politeness. In reality, one of anti-social behavior.