@Batora
It's not being "mature" or being responsible or similar of that kind. It's about the f*cking mood.
So tell me, imagine yourself being on MC's shoes, you planned a Christmas date, quite grandly if may add. Only to be ruined by unexpected urgent work, and you have to work overtime for that. So, you get home, tired and all, also the fact the planned date ruined. Additionally, your gf offered what is basically a "pity sex", a consolation of sorts, on your would be important first time as a couple. Basically, rubbing salt on the wound at your pride as a guy. How would you feel?
Also, there's a high chance of doing it half-assed 'cuz fcking tired of unplanned overtime work. You might not be able to satisfy your partner or you would've imagine you can do much more than that. Thus, unsatisfying yourself too.
Like I said from my previous comment: "Yes, blue-balling might be bad, but doing it half-assed is much worse. " Better not do it at all than half-baked.
From what I see, the Author is showing his vision of innocent romance of a couple. S/he isn't pushing an "sexless love cohabitation is better" ideology nor it is implied in any of the chapters. IDK how you get a speck of that idea lol. But I guess some you guys only see the inevitable sword and sheath play which is the main objective, and not the process inbetween.