TO ANSWER YOUR QUESTION, OBVIOUSLY.. BECAUSE IT'S THE BEST CHOICE...
way to comfort a sad prospective lover:
1. SEX (hot and effective)
2. HUGS AND KISSES (to mild and cute)
3. DRINK ALCOHOL (common way for drowning your sorrows which also ends up in bed scenes btw)
SO WITH THESE CHOICES.. DON'T YOU THINK THE AUTHOR ALREADY MADE THE BETTER CHOICE...!! IT'S YAOI.. TBH, THAT'S THE MAIN REASON WHY...
Having sex will not solve the problems that they have if this was in real life but seeing how this is yaoi then it's all a mere fujoshi's fantasy. But I have to agree with OP though sex does not really solve the issue instead they need to have an intervention with each other and release all the painful things that they've been keeping from their chest; be honest with each other instead of being a martyr and forget about it by using sex until the same argument comes back in the future again.

idk i just hate that common yaoi transition of "you're super depressed about a thing soooooo... here's some half-assed catharsis. oh and my dick in you. that parts important. gotta finish of important, emotional discussions with sex."
's always felt off to me. doesn't mean the story isn't cute, just irks me.