I studied and worked in marketing for a little while before becoming disgusted by it and leaving. The vast, vast majority of ads have a primary goal of raising awareness, not triggering a purchase. It's extremely hard (and often ineffective) to trigger a purchase, unless the ad is seen while literally standing in front of the product at the store. The best marketing technique is to raise awareness of the product, so that when the user thinks about their own need, your brand/product is the one they think of as a solution.