I would pay full price for Fallout 3, New Vegas, Oblivion if they would simply fix the bugs and re-release them to run properly on modern systems. (And I'm one penny pinching MF)
I would guess they don't do this because they're worried the community will freak out about the update breaking mod compatibility but they already kinda did this with Skyrim when they released the Enhanced edition or whatever they called it.
There has to be money on the table here for them. If modders can fix their games without access to the source code then it couldn't be that labor intensive to hire someone to go through the code and fix it right?
I just don't get it. Are they maybe worried the old games will cannibalize the audience for their new games or something?
I shouldn't have to beg these assholes to be greedy. This is America god dammit. 
I think it is just pure laziness. They've come to expect modders to fix their bug riddled messes with patches, the playerbase accepts that's how it's always been and so quality control only has to go so far.
I don't mean to look a gift horse in the mouth either but mods are a miserable solution. Annoying to install and often come bundled with crap you don't want and work in unpredictable ways.
I just wanted to play Oblivion with a pad but the mod that people use to add pad support comes with a full UI overhaul unless you go into the files and manually edit a bunch of crap that literally nobody has time for. Who thought that was a good idea? I'll pass on CrashFix 2.4 + Massive Milkers modpack thanks.