I'm not into SNDS, Kara and others kpop girlbands as before. Although my favourites are Wonder Girls
. But I can't deny that SNDS songs are likely the most catchy songs in kpop. GEE GEE GEE BABY BABY GEE GEE AAAAARGHHH GET OUT OF MY HEAD (
).
So maybe that's why they sell that well.
BTW it's just a trend, I guess. But it's quite sad for solo artists though ;_;