Yes and no. Technically any given advertising campaign doesn't need to be effective, only convince the buyer that it is effective (without engaging in fraud). But relevance is important to the ad companies because they aren't going to pay for you to advertise towards markets they aren't even operating in or planning to. To go reducto ad absurdum, you wouldn't get any ads contracts if you were to start advertising towards inaccessible alternative universes and alien planets when they cannot even buy the products. Even if it gives trillions or quadrillions of ad impressions that could not be any less relevant towards them.