When the system evolves, you need to change things. State structure also evolves and you will refactor and rework it. You'll rename things, move fields around.

URL is considered a permanent string. You can break it, but that's a bad thing.

So keeping state in the URL will constrain you from evolving your system. That's bad thing.

I think, that it's more appropriate to treat URL like a protocol. You can encode some state parameters to it and you can decode URL into a state on page load. You probably could even version it, if necessary.

For very simple pages, storing entire state in the URL might work.