It’s because roads are a trap since their cheap to build but expensive to maintain, and they all tend to need maintenance around the same time when you build a bunch at once. When that time comes around, you’ve got a gigantic cost to pay for resurfacing and Pothole fixing and the like, and the budget isn’t enough to pay for it. So some get fixed and the rest get kicked down the line. But the thing is, then other roads need the same thing and the same problem arises, and there’s never enough in the budget to pay for it all. And since roads and streets don’t even make close to enough money to pay for their own maintenance, you need to rely on government funding. But here’s the fun thing, in order to make enough money for those maintenance bills, taxes would have to be raised so high that people would be paying more than their entire yearly income on taxes alone, which obviously you can’t do. So the money never comes, and the roads stay broken. But since we’re all so far deep down the car dependency pit and the initial construction cost is the only number anybody looks at, we keep building roads that we can’t afford since it’s the only transportation option that anybody thinks we can build. And so the cycle continues.

There’s a great series on YouTube that goes into more depth on this, it’s by the creator NotJustBikes and it’s his StrongTowns series. Looks into how car dependant places are being subsidized by walkable/public transit focussed places. Highly recommend watching it