An excellent question. The "traffic engineer" profession is deeply broken. https://www.nytimes.com/2023/01/06/us/widen-highways-traffic.html
Widening Highways Doesn’t Fix Traffic. So Why Do We Keep Doing It?

With billions of dollars available to improve transportation infrastructure, states have a chance to try new strategies for addressing congestion. But some habits are hard to break.

The New York Times

We now have overwhelming evidence from a million different directions that sprawly car culture *doesn't work*. Suburbs don't pay for themselves. More lanes don't decrease traffic. Stroads kill people & inhibit economic growth. Parking is economic deadweight.

We refuse to learn.

@drvolts the problem with more lanes is that to actually resolve traffic you would need so many lanes the roads would take up more space than housing