Sure it would be nice to resell. But face it we've all saved a lot with digital download services, including Steam. As a collective whole we haven't been tearing walls down to make reselling happen, online always DRM gets one's emotions boiling much more. How about we just re-up again and support the industry and keep these personal collections, as it's benefiting use with lower prices and them with overall sales #'s. AKA it's working right now, don't F it up.
If re-sell became the norm, prices would go up or quality would go down.