Why do K-POP idols use -요 when they talk to each other?

I am curious about why K-POP idols still use speech that ends with -요 when they talk to each other. Many fans can see through various content that they have spent a long time together and have built a close relationship. Nevertheless, they often still use the honorific -요 with each other. This may be attributed to the cultural background of Korea. In Korea, even among close friends, there are times when formalities are maintained to express respect for the other person. This is especially pronounced in public settings or when many people are present. Due to these cultural reasons, I think idols might be using expressions that show politeness towards each other. What do you think about this? Could there be other reasons?