MC does not have anything to offer - in his life experience, girls have been leaving him for whatever reason
all the time. He is offering his pleasure to share his life and time with each and every one of them,
not anything like his cars, mansions, cabins, hotels, cohorts of servants or his yachts.
I hear what you are saying so point taken. For me, however, there are times when I am okay with harems, like harem hotel or desert stalker, but they seem to fit in those worlds/environments. This story is more realistic when you look at the setting and behaviors, so a harem would seem out of place. Part of it, too is as I play more of these, I have started appreciating a good story that has some drama and emotions. Harem stories all have women who will not cheat on the dude but are fine with the dude doing whatever. I can see maybe one of the women being like this, but for all of them? It never feels right to me. People, when emotions get involved, rarely are logical, rational creatures.
Don't get me wrong, give me a good old corruption VN any day, but I guess I have different ideas for different types of games, and a harem just seems out of place in this one.
Regardless, I see where you are coming from regarding the MC's behavior.