Questions: Society & Politics

Too often i see people responding to questions on here with “it’s not illegal, it’s fine”.
Most commonly to the notorious question “she’s 19, he is 43, is this okay?”
I can’t help but wonder do people not realize that not everything wrong is illegal. I’m trying to gauge how many people push their morals and ethics all the way to legality, if it’s not illegal, they’re doing it.
The 19/43 age thing is just an EXAMPLE. Not the topic here.
Better example, even: here in california, the law has been adjusted so that shoplifting charges wouldn’t be made unless it was for more than $900 dollars worth of merchandise. Would that mean any time you steal for <$899 worth, “it’s not illegal, it’s fine. the state consented”