At least in the US, their crime may well be something that doesn't obviously harm others (like possessing a small amount of marijuana for personal use, or consensual "sexting" among teens).

It might also make a difference if the crime was committed when they were very young, and they now clearly recognize that it was wrong and something they would not do again. I've never committed a crime or seriously harmed anyone, but there are things I did in my teens/early 20s that it find mortifying at 40.