Does the USPS need the DNM's to survive? I remember hearing awhile back about the USPS struggling to finance itself and how there was a chance the USPS may have to cease operations.
It seems reasonable to me to assume the growth of DNM's have had a positive impact on the USPS's bottom line. If this is the case, I'm sure the right people are aware of this. Does this work in our favor or is it merely an inconsequential side effect?
USPS survives due to ebay sellers and direct advertising. Ever pick up a change of address form and notice there's more advertisements in it than forms? Your theory makes no sense. DNM postage probably equals less than a few million dollars per year.