Serious discussion about mental illness is still a pretty big taboo for a variety of reasons. Generally, the beliefs are that nothing can be done to help, and that it's a result of personal weakness rather than biological factors or having fucked up shit happen to you. There's little exposure overall to counselors and therapists as people who can help; compare that to American TV where there are a fair amount of movie or TV characters who visit therapists. It's one of those situations where the elephant's been in the room for so long that it's started shitting everywhere, which makes people even less likely to bring it up, because then you have to acknowledge that there's shit all over the carpet, or in this case, that people are hurling themselves in front of trains on a daily basis. It's difficult to get into any more in-depth of an answer than that because much of it is bogged down in "NIPPONESE SHAME AND HONOR SAMURAI WABI-SABI"
