If ads were merely about being informative, they would be boring. But ads want to manipulate, so they have to be flashy and appeal to your emotions.
They pollute your mental headspace, and have no place in a healthy society.
Let's ban billboards. And then let's follow that up with a general purpose ban on paid advertisement.
The law is pretty consistent about the idea that any paid endorsement has to be "truthful". And as we've learned more about sociology and advertising, we've realized that things like paid endorsements are fundamentally not truthful, because they are misleading the public to believe that some figure or trusted source (even if only at a subconscious level - which is still enough to change consumer behavior!) is in favor of a product or brand.
So maybe if you could argue that paid speech is inherently untruthful (which I believe that it is!), then you could make legal policy that bans paid speech complaint with the First Amendment! (caveat: I am not a lawyer, I am not a legal activist, etc)