It sounds like your Dad sells like I do. I went from behind the microphone to sales and I thought I hated sales. My boss told me to go out and make friends and work for your friend's continued success without any worry about my own. I could wrap my head around that.
I am the same way about instant recall of, say the last commercial break on radio or TV and even if I pick up a newspaper to read a story, I couldn't say what ads were on that page. Likewise, the ads on the last website I cannot recall. I think it is safe to say all advertising is a gamble and that passive viewing/listening is more the norm than not. I recall a mail order guru telling me a 1% return was okay, 3% was incredible. How many ready that shopper that shows up every week, going to every house? Many just trash it unread. How about all those billboards you see on a trip down to the store, to work, etc.?
While the above does not paint a real rosy picture for advertising in virtually any form, the fact it survives and/or flourishes says it works. You mention Home Depot. You can bet if radio didn't work for them, they would not be buying radio. That can be said for any advertiser that buys any media option or advertising venue. There are only so many clients and if it doesn't work you are more quickly that we might suspect, out of potential clients.
Something I thought was interesting when I was doing radio sales in a community that had a fishing lake that attracted about 1.2 million visitors a year, I noticed a guy had just opened a boat rental shop. He had only been open a few days. We talked about where he felt his customer would come from and many other things. There was a fishing tournament coming up and I suggested he buy an ad in the state fishing magazine that was featuring a few pages on the lake and the tournament. Since he said he felt his 'bread and butter' was the local looking for a day on the lake, I suggested a small order centered toward weekends following the 1st and 15th of the month, when most people got paid. He bought. So, the entire marketing dollars went to an ad in a fishing magazine and my 'payday weekend' schedule.
He said he was going to ask every customer where they heard about him. I cautioned him about results. I told him people didn't remember. I showed up after the fishing tournament to see how he did. He did well on those payday weekends and the tournament. The results of asking people where they heard of him, well, the magazine came in first because he had a cut out dollars off coupon. Radio got zero responses. Second was the newspaper (he never had an ad in the paper) and the Yellow Pages (he was a new business and not listed in the phone book...this was pre-internet). A couple said TV (no ad there either). Looking at his sales, he could see big spikes around the 1st and 15th. Sure, those days were 'prime time' for renting a boat but there were many long established and bigger boat rental shops so I felt good about the results, figuring his advertising had paid off pretty well. He felt the same way.
I did make a huge mistake in sales (before I learned sales). I was told to go get the local Dairy Queen on the air. It was suggested the lunch special be the product advertised. This DQ used to run an off menu lunch special as an all you can eat buffet. The client suggested we run a special where the radio listener said radio to get a big discount (half price). I ran a heavy schedule with lots of bonus spots. I could see the DQ from the station. The parking lot was full and people parked along the street for a block or more, something that never happened. After it slowed, I checked on results. Yes, they ran out of food an hour in to the special. It was the biggest lunch run they ever had. In the owner's mind radio didn't work because nobody asked for the special. I never got another dime out of them and could not convince them the busy day was due to radio. Why did people not say radio to pay half price? I think most were not confident enough about how to get the discount to demand or mention it. They did remember the place and what the meal was. When given the price, I'm guessing they thought they heard the price wrong. I can't say exactly why. I can say you're doomed when you make the listener mention radio to get the deal. I suspect the same goes for other media unless it is a printed coupon you present.
I used to love it when I could get a local advertiser to let me develop a series of spots centered on characters. I had a barbecue restaurant that did. There was the man, his wife and Tripod, his 3 legged dog that sounded like a gorilla and always wanted a barbecue burrito and a beer, and the mother-in-law, which always caused the old man to buy a family pack that would feed 4 because, as he would tell his wife "You know how your momma eats". People used to call to try to get their pet on the commercials and people would call to request we play the commercial. I always though it was silly spots but it took on a life of its own. The owner even held a Tripod look alike contest! Then there was the pest control guy that let me carry on the saga of Bubba Bug and his brother Stinky Bug, the meanest, oneriest and biggest bugs in the west, that made the other exterminators shake in their boots. By no means are these stellar but unusual and greatly aided the business in gaining new customers and they continued to buy for years. In fact the pest control place would let me know where local infestations were happening and we'd tag the spot with "Bubba was last seen near the corner of X and Y streets. If you see Bubba Bug, you know who you gotta call" (think old west saga here).