Soju is #1. Your face is plastered all over Korea.
That I think is a major reason for IU's dominance in SK.
She has been the face of Jinro Chamiseul, the most selling Soju, since 2014/2015.. With only an year's break.
Jinro until IU rarely repeated models even for two years, yet she is on her 7th year.
Hence everyone who gets 'plastered', gets to see her face plastered everywhere.
Pretty much every eatery..
Suzy also but to a lesser extent with Chumchurum, replaced by Jennie.