Koreans are starting to use English names in the office because it's easier than just speaking their own language

TLDR: Korean has all kinds of really convoluted rules about how to be respectful to your superiors. (It's bad enough that it's what made me give up on learning it.) One of them is that you can't call them by their name. Normally you would use a job title or some term of respect.

So who is your superior? It's not just your boss, it can be as petty as them being a few years older than you. So there's a major pain in the butt when two people meet where you have to subtly work out between you who whether you're equals or one of you is on a slightly higher level.

So in order to skip that bullshit and have a culture that's less obsessed with seniority and age, the hip new startup companies are having their employees pick English names and use those instead. Tbqh I suspect it's more because they think being Vivian or Bradley is cooler.