You don't know that a purchase decision wasn't subtly influenced by seeing a Youtube ad though. Many ads aren't designed to get you to buy a product right now,

You don't know that a purchase decision wasn't subtly influenced by seeing a Youtube ad though. Many ads aren't designed to get you to buy a product right now, they are designed to make you feel a certain way about the product or even just make you aware, so that when you are in the market, you are directed toward that product.