Foxhack: This isn't a matter of "If I don't buy it at Steam I won't be able to get the items."
I just find any game that includes TF2 items to be... horribly... suspicious. It's a way to ensure a moderate amount of sales on Steam. It also makes me lose confidence in the quality of the game.
Given some of the last few games to do it were Total War: Shogun 2, Plants vs Zombies and Mount and Blade I *really* can not agree with the 'lack of confidence' thing :)
It's a marketing ploy, simple as that. But not necessarily for bad games. Heck, it's probably nice for both developer and Valve. Valve gets some more goodies for one of their games, and the developer gets some more sales from freaks like me xD (though I don't think I'll be getting many more full priced games just for the goodies xD)
I got Homefront 2 (bad one to be fair) and Shogun 2 for the goodies mostly (and I wanted Shogun 2 to some extent) and with the goodies I basically paid off both.
But the market is crumbling at the moment with the massive influx of hats. So yeah, getting less and less likely for people to buy for that.
Edit: Omg nooo... they're scout items ... :( I love scout