It may seem that way to you but it's really perfectly logical and just.
Let's say someone steals something from you, let's say your statue of the Blessed Virgin Mary that is on your front lawn, (just trying to lighten things up). A short time later the thief feels remorse, he returns to your home, admits his crime and begs your forgiveness. You agree to forgive him, you get on the phone to the police right away and tell them that you don't want to press charges. The repentant thief thanks you and begins to walk away. Now, what do you do, just let him walk away? Of course not, you say, "hey, you still have to bring back my statue!"
Does this demand of the thief somehow lesson your gift of forgiveness? Somehow lessen the gift of not having him arrested and put in jail?
If you never required him to return the statue, do you think he would be less likely or more likely to appreciate your forgiveness? Don't you think he may start to think -"Oh stealing from this guy is no big deal, not only does he not have me arrested, he doesn't even want me to give back what I stole, he doesn't even care about what is rightfully his, it can't be that valuable."
Do you think he may be less likely or more likely to steal again, if he is never required to give back what he steals?