I believe the rationale is even if say 90% of the viewers who wouldn't buy the product anyway are now less likely to buy the product, That's considered a zero.
However if you're positively influencing the purchasing decisions on that remaining 10%, then it might be money well spent.
Thus the advertising may not affect specifically you but because this is a broadcast style exposure, that doesn't matter
IMO it is quite like the classic example of the heuristic that there is no such thing as bad press.
Some of the most life-changing products I own were shown to me in an ad. Might not have bought that exact item, but the knowledge of that type of product even existing?!
Mindblowing.
Otherwise, Firestone should have seen an increase in tire sales after all the free advertising they got on the news. Instead, though, Firestone tire sales fell off a cliff.
I recently threw away a coupon for a product specifically because I saw a few too many extremely annoying online ads for this product, and now I can't stand the brand. They poisoned my image of them.