Technically, you get a benefit of a potentially huge discount (usually 75%) for a random game if you craft a badge. However, in order to craft the badge you need to either trade cards with other players (which can be a slow process), or buy the missing cards on the Market with money from your Steam Wallet. A percentage of money from each purchase goes to Steam, most of it goes to the seller.
Naturally, the discount you get is usually for some indie game (which is not that bad), but given that Steam is now publishing pretty much any game on their platform, oftentimes you end up with some discounted crap that you wouldn't be playing even if it was free. Other than that you get some cosmetics - the aforementioned badge, profile background, unique emoticons to use...shit like that.
tl;dr For 20-50 cents you get to edit your profile a bit. So yeah, it pretty much does nothing.
I've been ignoring that thing for a while now, but some time ago decided to gave it a try and I traded some cards, sold some, bought others...and yeah, it's pretty much useless. Sure, my profile looks pretty now, but who cares?
As for the OP, it's never going to happen. Bethesda has basically dropped all support for FO3 and FNV, no way they'd bother implementing some gimmick on Steam just for the sake of it. At this point, they'd get zero profit from it. Even if they were to introduce a feature like that, Skyrim would be a more likely title to get the honour, given that it is a newer game and has a bigger base of players, but I think that one has no chance of happening either.
That being said, it's not impossible that future Bethesda games will have these things implemented. In fact, it is highly likely, given that it is a rising trend, both among AAA and indie titles.