Why do you say that? I realise we're guessing as to the terms and conditions of his loan to us, and of his move to Preston or wherever, but as I see it the loan has worked well for all parties. For MFC he came in to the first team and made a positive contribution. For Man Utd, they're presumably reducing their outgoings on wages (and / or getting a fee) for a player who's unlikely to get into their first team. For the player, he's shown himself capable of first team football at a decent level, and presumably got a good contract at the end of it.
I'd much rather loans worked out like that than say like Jake Taylor's, where no-one has got much out of it.