It's more complex than that. If we have words on the street, and I punch you and break your nose, you won't have any problems getting your complaint taken seriously. Nobody gets their nose broken for pleasure; even boxing clubs and so on have rules of conduct and activities are generally supervised to ensure conduct remains within those boundaries.

On the other hand, people have sex for pleasure a lot, and sexual activity is strongly linked to emotion, so if you come to the police with a tale of an unwelcome sexual encounter you have to answer all these extra questions about consent and secondary motive to get taken seriously. If a complainant doesn't show obvious signs of physical trauma indicating a violent struggle, then it can often be a problem to get the complaint of rape to be taken seriously and investigated urgently.

My impression is that in many countries, police officers are inadequately trained and often do not treat rape and sexual assault as seriously as they deserve.