Letting people communicate freely is a good thing in its own right, and fundamental to so many other good things we enjoy. Getting rid of a billboard for something I am never going to buy sounds great, but it kinda sucks for the person who actually is interested in the thing that billboard is advertising. Even if there were some type of advertising that provided no benefit to any part of society, the restriction on the freedom to communicate those advertisements is something that harms all of us.
Sometimes the part of building a better world that takes the most effort is recognizing where we already have.