I know your question is probably rhetorical, but the answer is that advertising isn't really about persuading people to buy something specific. Its about creating an association in people's brains, so that the next time you think about toilet paper, your brain automatically thinks "Charmin" and your decision making changes from "what brand should I buy" to "why not Charmin".

The more times they yell it at you, the stronger the association gets. They don't care if you like it or not, they want to train you like an animal.