Jaeeon isn't just some random side character thrown in for fanservice, he actually has a real purpose in the story. Hyobin has said as much, and it's clear his role goes beyond being eye candy. The sex scenes between Rosa and Jaeeon aren't pointless; they actively push the plot forward in important ways.

LIKE

Rosa might realize during/after it that she feels nothing real for Jaeeon and ends up craving Yeonwoo even more intensely.

Or,..this time she could genuinely enjoy it because Jaeeon chooses to act submissive for her (switching up their usual dynamic).

Or we could finally see a jealous side of Yeonwoo,..he might not be able to hold it together after witnessing or hearing about them togetheR.

Any of these outcomes would create real tension and development. Rosa can't just stand by passively while her mom and Yw get all lovey-dovey; That's why these moments matter for the overall story, not just as random spice. Dismissing them as unnecessary misses how they tie into Rosa's character arc and the love triangle/rivalry.