I used to think that way, and I can see the argument for having players fully signed up and committed, but increasingly, I don't think it really matters.
I imagine a player like Hodson, for example, will have plenty of motivation to prove a point or two. Whether he wants to re-establish himself in the tribute act set up, is trying to secure a permanent move to Saints, or is simply wanting to put himself in the shop window, it's all good.
That could well be preferable to a player coming in on a permanent contract who is quite happy to have a deal for a couple of years and that is his main aim.
I also mentioned in the other loan deal thread that it opens up markets that we could never realistically expect to access otherwise. If (a big if, granted) we manage to bring in Johnson from Shellick, we can rest assured that we would never have got a sniff had it not been a loan. Likewise numerous others we have had on loan (at least initially).