While some ads drive impulse purchases, much ads are getting brands into your decision consideration. E.g When you need something of you have 100's of options.

While some ads drive impulse purchases, much ads are getting brands into your decision consideration. E.g When you need something of you have 100's of options. If you saw an ad previously it now might be 1 of several products you compare as you are aware and familiar. The product still has to impress you on price and quality etc but the ad drove you to consider it. That is hugely important in a crowded marketplace. Also that ad might have shifted you perception of quality or features. And ultimately 'need' is a very subjective thing. I highly doubt if you look around your house there is nothing you couldn't throw away and not get on with life as normal. Ads can make you feel like you need something at the time. That's why so many ads rely on fear based propositions, this emotion is strong in creating need like showing negative events for insurance.