I never had the chance to visit the arcade for quite some time already. When I was younger I used to play King of Fighters and Tekken and even joined some tournaments when it was not that famous it was a bliss memory of mine.
Right now, same with your observation, arcades isn't that crowded anymore probably because the students are not going there as they have their own mobile devices already? Not 100% sure but most likely it is the case.
I think it is because of that, in fact having so many facilities to meet online nowadays, makes less students or young people go to the machines, it seems to me something natural to happen, although it hits hard on nostalgia to see this place empty when before it was totally crowded.