Seriously, it's the girls who bring what Bakarina needs in life: gardening, doujin and food.
What do the boys in her harem offer? Zilch. The fiance wants her around because he finds her interesting, a spice for his boring life. Her adopted brother is an obnoxious obsessive siscon who does all he could to cockblock the fiance. Alan plays music that she appreciates but doesn't care that much, and the emotionally stunted Nicole is nothing more than eye candy. Waste of space, those boys are.