Shower thought: maybe the emo/scene movement of the late 00's was brought about and strengthened by the global financial crisis. Dark times were reflected in youth subcultures, and popularized by nascent social media trends.
Discussion
I don't know where you are in the UK but at the moment it seems everyone wants to paint their houses/offices/shops grey and black. I liken it to the national depression at the end of empire in the 60s when Brutalism in architecture was a thing. Your observation about the emo thing could be another indication of a sort of collective depression in a similar vein.
Or even if your in the UK. I worded that badly.