you're losing a lot of fans that way.
honestly, that's a big mistake that a lot of kpop groups make when promoting internationally, they always forget about their Korean fans. and when (expectedly) they fail to actually reach popularity internationally, they have no where to fall back on.
And while yes Blackpink is definitely popular enough internationally to get by without Korea, it would also be a huge loss to abandon it completely. a lot of their sales still come from Korea, and a lot of their streams still come from Korea. hell, they are THE girl group in Korea right now with each member being popular enough to make it solo and be successful. abandoning your biggest and most stable market for a smaller one that shows potential, but is risky, isn't the best idea.
not to mention, if blinks wanted to go listen to a girl group with all English songs, theyd go listen to little mix or boys world. blinks like Blackpink BECAUSE they are kpop, because they speak Korean and show their background in their songs. if they've made it this far with Korean songs then why should they stop, it pleases both audiences so there isn't a need to.