The RFID came more because of people bringing back old mugs or even Big Gulp and other non-Disney glasses to use trip after trip. It is still fairly easy to share with the RFID because the lockout is pretty short - I think a minute or two - but you do at least have to buy one mug now.
Ah, but that assumes they *need* to be that cheap. For a lot of people, this sort of "extreme frugality" almost seems like a game. They could afford the sodas, but why pay for 2 (or more) if they can scam what they want while only buying one?
Our movie theatre gives away brown paper lunch bags for that! They introduced them at the same time they started offering the whole menu of crazy flavor toppings, which I really appreciate because there's no way I'm buying two smalls @ $10 vs one large @ $7 just so my kids can have siracha-cheese-ranch popcorn. I guess the popcorn is that low value to them or the time-limited nature of the movie experience is enough of a hedge against extremes, that they're not concerned about the bottom line impact of sharing.