Our culture values the act of buying things for social status (consumerism), and one of the main reasons for that is advertising.

You're assuming people would still have the same amount of money, but for most money is not a given, and people strive to earn money precisely because they want to buy the things they were advertised.

Without the social pressure to acquire things one doesn't need, it's very possible people might simply work less and use that time for other things.