One of the most annoying things about spam is that it works. The cost is so low that a minuscule conversion rate justifies the expenditure.
Similarly with direct marketing. I saw a couple of guys yesterday sticking restaurant flyers through letterboxes on a nearby estate and was reminded that on a monthly basis, I get similar stuff drop on my mat. It's mainly from a pizza joint not quarter of a mile away that I will never frequent - not because I know anything about it but because it's a quarter mile in the wrong direction for me.
But the business keeps sending out the flyers and presumably feels justified in doing so. Regardless of whether they track sales against flyer cycles (which I doubt), they're engaging in marketing and this is what business are meant to do. Or is it?
I am aware of the pizza joint not because of the flyers but because I've driven past the place a few times. The flyers have no effect on that and, for reasons previously stated and totally beyond their influence, will not change my behaviour. Does advertising your presence to people who will anyway become aware of your actual physical presence during their regular lives ever have a positive effect? Maybe, maybe not.
But, unlike spam, I'm sure that marketing spend could be better directed.