Maybe you're someone wholly untouchable but advertising is accompanied with thorough independent market research and sales numbers and companies can directly see the impact of their ad campaigns. It's indisputable.

In the long term it's also about brand recognition, you see a "stupid ad" today and in a year when you're looking for that kind of thing you are more likely to choose that brand over another and you don't know why but "this jams seems better". The effect is proven, scary and it's something we're relatively helpless against. It doesn't help that our brains sometimes register things running in the background on the TV while we're petting the dog. Product placement in movies works like that too, if we notice it we think it's obvious and stupid, but we still notice it and even when we don't notice it our helpful subconscious is right there helping us remember.

Moving into even worse territory, on social media like Facebook they can profile you enough to know where you're leaning politically and if you're not entirely confident in your political stance they can show you ads that looks like product ads but are designed to nudge your political stance a bit to the side in the desired direction.

The effect of ads on the subconscious is scary. It's not mind control but it's can influence you.