Full disclosure: in my student days I used to work for a direct mail company, not as a programmer but as a general layout and graphics guy. They weren't mail spammers per se, they specialized in hospital funding drives, or did mail followups on people who were on prescription drugs, to remind them to keep renewing.
Anyway these letters were tested just as carefully as we do today (only an A/B test involved actually printing and mailing stuff). The "Yes! I want to know more about $FOO" format may seem cheesy but it was a proven winner.
You would think people might get tired of it, but they believed that their targets were instead "trained" to respond to these sorts of appeals. That's literally what I was told, when I suggested they try something different.
So, maybe we should be paying close attention to those crappy cards that fall out of magazines?
The idea that direct marketers have something to teach us also probably spreads because it's counter-intuitive: you mean all those icky ads I grew up with were clever?