They could set up something like an App Store where mods would have to be approved and then they can charge console users to get them. I think they'd make a lot of money if they did it. Just lock the downloads to one specific site that Bethesda controls.
After seeing the official reply:
This game has at least 7,000,000 players. If only 1,000,000 of them download mods, that's is a LOT of money. Bethesda should straight up hire one or two guys who ONLY work on mods as DLC. They would pay for themselves within a couple months.
Moderators are volunteers, we aren't employees, so my comment shouldn't be considered official in any way, shape, or form.
Even if Bethesda has the resources to select, test, and prep mods to be officially released there are other problems to contend with. Chiefly, they need to test how mods interact with eachother and how the XBox 360 and PS3 handle large numbers of mods. The former issue gets more difficult as they release more mods, and unless the latter has a very high ceiling Bethesda probably couldn't release many user-made mods.