Ironically they also have a sign that changes, one of the updates is “don’t drive distracted”… and like, I wasn’t distracted until the sign flashed at me lol.
Good org on the other side of the issue: Scenic America: https://www.scenic.org/why-scenic-conservation/billboards-an...
I even saw a "you should be looking at the road" ad on one of those billboards.
This removes much of the incentive for spamming enormous signs and renting them out to the highest bidder. That may change if it becomes really cheap to put a functional vending machine below.