to me, what's the difference? He's either rotting away on my inactive list or playing terribly on someone else's team (which could be a benefit). No matter what, at that point he's not going to help my team compete.
If he's a terrible player in the last year of his contract, and I only release him after I've played him half a season, how much am I really saving by keeping him around? It's useless cash at that point. Say he was under contract for $4 million...halfway through he's now only due $2 million. After the transaction deadline am I really going to find a use for that $2 million I could save by trading him?