It does seem bizarre but it is quite logical. For Verizon, they don't really give a rat's ass about you until you sign that two year contract, because then the tables turn completely in their favor.
Take for example an existing customer who's been off contract since, say, January and paying month-to-month, but still has his NE2 discount waiting for him to pull the trigger. It's not just because he's off contract that he's not able to go into the store and use that subsidized discount upon signing a new two-year deal. Of course, your mileage may vary in that you never were contracted with them with a data plan on your account, so they could come around with their corporate paw and put an end to your shenanigans, but such is the risk you take for trying to play the system.
After all, how dare you eat the cake and keep it too? Only VZW can do that