One time Harley got cleared and released from Arkham only to have a series of unlikely events drive her over the edge into putting the suit back on. Batman rounds her up and sends her back to Arkham, of course, but the sentiment between them is that he's glad she made it this far and hopes that next time it will stick.

Batman cares. It's just "supervillain redeems and goes straight" doesn't do well when they inevitably have to go bad again in the neverending story format of modern comics.