I wouldn’t so much expect it to be prosecuted as a crime as widely eschewed by parents and governing authorities who respect the laws of God and nature. My employer has been known to fire people who are known to cheat on their spouses. Adultery lends to instability and, if rampant enough, diseases. We don’t encourage that kind of behavior unless we are reckless, lawless, and godless. None of those attributes attend to good government, but they do appear all too often in bad government.
It is certainly a sin, as you note. It still meets with social disapproval. It has been pushed as “victimless” for decades now.