One silly(?) idea I had was that the pre-war IRS (or its Fallout equivalent) had their own AI at some point, made to keep tabs on taxes owned and collect them in any way by whatever means are available. I think I called it some silly name like Taxatron, TAXER or TAX-MAN. Anyway, after the war, the thing is re-enabled. It looks at its own internal calendar, sees that it has been over two centuries, starts doing tax calculations... and promptly goes after anyone "in debt". Its intelligent enough to know a nuclear war has happened, but its programming is also strict enough that it can't stop making people pay tax, even through the United States doesn't exist for a long time. So there's this AI that simply goes around and tries to collect two hundred years worth of extremely overdue unpaid taxes in current's day currency from everyone, simply because its programmed to. Of course, it has the robotic muscle to back it up. The Player Character is The Dodger. He/She is literally the first guy to get a visit from the "Collectors". The (Tax) Collectors are Taxatron's enforcers in the matter of tax collection. They WILL take your money, and if you have no money, they will take your stuff. This makes them stay away for a while, but they WILL come back and take your shit again, unless you can find a way to fight/avoid them. The problem is that this is literally destroying the region's economy as Taxatron takes everyone's money and/or goods for its payments and does nothing with it. It won't attack cities brazenly, but that's about it. Essentially, the first part of the main quest is to stop getting your lunch money stolen by robots, or pay it off.