Eh, he has a point. There is not much precedent for reselling or trading digital goods back. And if they were tradable, it would increase value of the product, which might be a bad thing. I think being able to buy a pack of 12 games for 5$ at the next sale is a better deal for me than having to pay full price but being able to trade it back for some discount.
And game publishers are working to thwart the used games market as it exists for console titles, so things seem to be moving in the opposite direction in general.
I have a load of steam titles I would trade back if I could though. There's some good in there, but also an awful lot of crap.