That's not necessarily how ads work though. Who clicks on an ad anyway? But a few months after seeing it, you're looking into buying something and you remember the brand or website from the ad you saw. Or heard on the radio.
Incidentally, I know someone who quintupled a company's sales in a foreign country subsidiary in a few months by increasing ad spend. The upper leadership in the home country was against it since "we have a strategy and it works" but since he took control of the subsidiary, he could take the risk and disobey orders. Back home it's a known brand already, but nobody knew it in that particular target market.