It's not that I want the world to function in that way, it's that sex is such a fundamental part of our biological nature that I believe it supersedes any human abstractions we place over our animal nature; to the extent where, the unworkable symbiosis you posited, of porn associated with the advertising of well known brands, is wanting the world to work in a different way than it actually does. More succinctly, just because advertisers haven't done it well, doesn't mean it can't be done.
In fact, as this generation of baby boomers dies off, I have a strong feeling porn will become far more normalized and have more prestigious non-porn brands associated with it, so long as more prestigious porn brands can rise up.