I seriously... just don't get it...

‌Yesterday evening, I was waiting to cross the street near Hongdae when about three motorcycles pulled up on the road.
The motorcycles were all heavily customized.
But they were playing music so loudly that the entire street was vibrating.
Sigh, do they really think that looks cool? I was wondering why they were acting like that.
The sound was echoing so much that I couldn't tell what the song was at first,
but the music was strangely tacky.
It sounded like something from a nightclub 20 years ago...
They were all nodding their heads to the rhythm, thinking they were all that.
But when I listened closely, it was a Chinese song....
Why on earth do they act like that in another country? Without any sense of public etiquette?