He is handsome and muscular. He has a tragic past and broods. He is considerate while still being DTF. He's pretty capable despite his meager talents.
I knew guys like him and they ended up with hot wives. Shirou gets a harem because the orbiters are crazy and don't mind sharing.
>>713339426 (OP)
Maybe in Japanese culture a man like him is attractive.
From what I hear being reliable and practical over there are good qualities for men as opposed to the west where it's more about being charismatic and outgoing.