I've wondered the same thing many times. The ads seem to be counterproductive. Another ploy they use is to repeat their phone number or web address far too many times during the ad. I understand the importance of being able to contact them, but to hear "That's 1-800 blah, blah, blah" or "That's www dot blah, blah, blah" six or seven times in a row is really annoying. I won't patronize a business that uses that tactic.
Well, that's my rant for a Saturday morning. Sorry for getting away from the thread topic.
It is the result of some study that the phone number has to be repeated three times in quick succession for people to remember it. It just makes me switch off the radio and I may not get around to turning it back on.