"Oh, let's tell our soldiers to not feel attracted to the sentient, talking creature we're asking them to bond with. No way one of them is ever gonna want to have a closer relationship with it if we explicitly tell them not to!!"
"Yeah, and there's also no chance the dragons, that are sentient and can talk with their riders, will ever want to fuck the person who took care of them since their birth but is not related to them!"
"Of course! And just to be sure, lets give male dragons to female riders! No way they're ever gonna be interested in the fact that the creature they spend all their time with and have a deep relationship with has a huge dick!"
I like how the dragon fucking and killing their comrade in arms that they raised themselves just for their meat happens so often they had to make a commandment about it. If a knight's order can be so deranged I dare not to think about what the rest of that world is like.