They choose that sexual relationship over a spiritual and romantic one because that's the society they were brought up in. "It's all he/she knows," meaning they didn't see anythign wrong with it, but later in the song she repents:
"And she wipes her tears back as she sings
How broken hands make broken things
She sings
Yeah, she sings"
A beautiful song, even better live.
They choose that sexual relationship over a spiritual and romantic one because that's the society they were brought up in. "It's all he/she knows," meaning they didn't see anythign wrong with it, but later in the song she repents: "And she wipes her tears back as she sings How broken hands make broken things She sings Yeah, she sings" A beautiful song, even better live.