Wrong. More lanes doesn't lead to more traffic unless there are way too few lanes in the first place. I know of plenty of places where adding more lanes would not add more demand - North Dakota is full of them for example.

The only problem is we can't afford to build enough lanes. There is a limit to how wide you can go, and up or down is vastly more expensive than at grade. We could do it if we wanted to spend the money - but most such places find that a better bus and (not or!) train network is a better investment.