There are people who attend one networking meeting and then give up because they "didn't get anything out of it." Usually they mean they didn't get any business as a direct result of that one single event.
Do they create a TV ad and run it just one time? Do they buy one radio spot and then announce that "advertising doesn't work"? You can't even test this theory because no radio or TV advertising salesperson would ever let you buy just one ad. They don't do this because they want to sell you more ads, they do it because they know that one single mention isn't going to get any return on your investment. Marketing, brand development, and awareness need repetition.
Sure, you might get that one or two people who were just waiting for an offer exactly like yours. This happens in networking events often enough, I guess, to reinforce the belief that it should take place every time.
I will never forget hearing someone grumpily announce at a meeting, "I've been here twice and I still haven't got any business from this!" I wonder what kind of advertising he does? And what he expects from it?