But if you have to choose from two clothing brands that have similar quality you will be more likely to choose the one you have seen in an ad. Even if you are only 10% more likely to do that (arbitrary number) multiply it by thousands of people and it’s worth it for the company.
That’s why ad companies are trying to get as much data as possible on everyone. They know that showing you random products won’t work.
They likely aren’t concerned, since probably their data shows that while a few people might be annoyed and choose not to purchase, overall sales would still increase compared to not running ads