Ads are most about mindshare. You probably don't need this thing now, but we are going to remind you x product exists and its AWESOME!1!
Cue some time later you need a thing and oh hey x product exists and then you go out and buy it.
I tend not to need things and I tend not to view media that has ads but i'd obviously be wrong in thinking that ads don't work on me. They work on everyone. Some ad somewhere has caused you to buy a thing and you probably don't even know it.