The kind of people who ran coupon schemes in the pre-internet days could have told you this. Back in the day, coupon schemes were things like you had to physically cut out and mail in vouchers from newspapers or magazines, and you got a discount on something like groceries in return. The point of this was market segmentation: you want to get people who (1) otherwise wouldn't buy your product, or at least not as much…
I'm actually sort of curious why, sometimes substantial, mail-in rebates seemingly largely went away? I haven't seen one in years. A significant customer of a former employer processed a lot of these out of Minnesota.
Probably not the reason they went away, but I do wonder how many customers were lost from bad rebate programs or rebate program mistakes.