Generally almost everything also has positive consequences, so you have to take both the positive and the negative sides into account.
Ads are not the only way to support free content, and in most cases free content is paid for with advertisement (at least not amounts you could see as a payment).
On the other hand ads lead to consumerism, overconsumption, poor spending habits, waste of resources for the adverts and the products they sell, and they reduce our attention to things that actually matter (like the traffic while we're driving cars).
Ads are not the only way to support free content, and in most cases free content is paid for with advertisement (at least not amounts you could see as a payment).
On the other hand ads lead to consumerism, overconsumption, poor spending habits, waste of resources for the adverts and the products they sell, and they reduce our attention to things that actually matter (like the traffic while we're driving cars).