Why do people often say ‘you’ll understand when you’re older’ instead of explaining things in the moment?

Because it’s a cop-out for adults who are committing or want to commit bad behavior or unethical acts and not be called out for it.

Every bit of the “you won’t understand until you’re older” stuff told me to when I was a kid was bullshit. None of it was true. All lies. All was designed to manipulate me and others. And I think that’s almost always the case with this from everyone everywhere.