Cause there was no reason for him to change in the first season. Kim Dan was whipped, did anything that asshole wanted cause he's a good person, he caught feelings and would essentially never go against JK. Jk wants everyone to submit to him, do things the way he likes, he has zero flexibility and doesn't take no for an answer. It seems like the second season is setting up a redemption arc for him seeing how Kim Dan is treating him and how he things he's being "clever" with inserting himself into Kim Dan's life. So there's a big chance we'll see him grow this season. Maybe he'll be less emotionally constipated too
jaekhyungs personality is so shit it genuinely pisses me off LOL how does he have absolutely ZEROOO character growth after 61 chapters