I think that the "modern culture" or what people want to think to be the modern culture; has already adopted that songs should be about sex, drugs and gangsters and stuff. If I would tell my friends/classmates/family that I listen to Japanese songs, they would think that I went crazy into one of my animes I'm watching currently.
Everyone finds it the standard to have songs with kinda harsh and darker toned lyrics. When I (for the first time) went on internet to check one of her songs' lyrics. (that was Rule), I also thought ; huh what the ... I found it to be weird (and childish a bit)
But that was because I listened to songs from Usher,2pac (i typed 3pac haha), kesha, chrisbrown, rihanna and stuff so you are not used to this kind of lyrics.
Anyhow, now they grew up on me and I love it

. Although I think that it's time to step up from the "sad songs" lyrics especially the "we were crying weren't we" kind of lyrics.