Just a speculation but from all we know for now he doesn't really want to be a crown Prince. Just like he said it's like "wearing clothes that doesn't fit". I believe Courtney and being sub is his only way to run away from all expectations people put on him since his mother passed away.
This manhwa always delivers ლ(´ڡ`ლ)
Ok but on a side note, I like that we're getting to know a little bit of Richards backstory, like there has to be something motivating him to be a sub