>I wonder why society decided that advertising was so important, it was willing to let it completely dominate (and in my opinion destroy) our public spaces.
Because advertising is a form of speech, and society has decided that speech is important?
All freedoms are limited by the freedoms of others. You may speak what you wish, but when and how you speak it is limited.
You can not scream about it in the middle of the night, since doing so bothers your neighbors.
Letting anyone and everyone do what ever they want would lead to anarchy. So no society, USA included, does this.
But some actors in societies have convinced the western population, especially Americans, into the fantasy of "freedom without limitation", which, just so happens to only apply to the rich and powerful, while everyone else has to contend with limitations on their freedoms.
I think you mean chaos rather than anarchy. Anarchy involves maximizing freedom for everyone, not just one's self, among other things. The strong doing whatever they want is the exact opposite of anarchy.
Because advertising is a form of speech, and society has decided that speech is important?