You are president of the world, and you have 5 men left. You need them to become aroused and breed, so who are you going to surround them with? Agents, bodyguards, nurses, they are all potential candidates to appeal to them, not just the women in the catalog and bath house. Even the women outside during the car ride could be staged when you're only managing five men in the entire world.
I see you've replied to a lot of the comments on here. And judging by the nature of your comments your name "Dr.Scientist" really suits you. What you said makes sense though. It could be what you said, or also that nobody would wanna read a harem manga where all the girls look ugly.
Look at someone you find attractive and pay very close attention to the sensation you feel in your head. That pleasant feeling, that magnetism for your eyes, that's your brain releasing chemicals in its reward center. It's positive feedback that makes you want to look and to keep looking.
To a lesser degree, it works even when that person is drawn. The whole objective of art is to draw your eye, and that's what attractive people do.
Sex sells, as the saying goes. If you go overboard, though, it can ruin the immersion and suspension of disbelief that is vital to a story's enjoyment. A story where the aesthetics make sense is win-win.
As for my name, hehe, thanks. A name should be apt, no?
And it just so happens that all the girls left in the world are beautiful and most even have elephant size titties that threatens to explode through their shirt (=・ω・=)