I'm with Lalita in that the whole J-Nuggs angle is pure speculation and not worth the paper it's not printed on.
Tossing in one J-Nugg a month or something similar as a lottery would encourage some new memberships, but piss off the older members - before the newbies jumped aboard, they would have had better odds of winning one. Either way, the odds would still be very long, and I think many people could find better ways to spend their cash than hoping they'll get a J-Nugg with no guarantees of any kind.
The simple fact is that the program's sort of a "loss leader" already - you'll likely get more than your money's worth over the course of the year, but you're giving it to them in a lump sum that they can use immediately. It's like you've given them an interest-bearing loan with a 12-month term, payable in playing cards!
They may have paid as little as $3 a deck for their supply, but as has been stated already, one J-Nugg could retail for more than three DOTM memberships! It makes no financial sense whatsoever for them to give them in DOTM rather than simply selling them, even in small or singular amounts. Say what you want about the Buck twins, but they know how to make money.