It's because modern advertising's purpose isn't to tell people about a product they already wanted but didn't know existed (which would be fine), it's to cause people to feel a sense of fear/loss/inadequacy that they previously didn't and then present the product as a solution, or associate a product with something people love in a manipulative way, because those types of ads are worlds more effective at driving sales. That's cancer capitalism and a lot of people with principles rightly refuse to be a part of it.