If it is all about the $2 for a drink then there is a problem. Disney is supposed to be the happiest place on earth, so don't ruin it for the rest of the people who want to go there and have fun.
Suppose a family of four each has a beverage in the morning. At $2/beverage, that's $8.
Now suppose they come back for a quick lunch break, and once again, there are another 4 sodas. That's another $8. I'm guessing that the paper cups aren't supposed to be refilled, so let's say 2 of those 4 want another drink and are honest. That's another $4. So far we're up to $20.
Same deal upon return to the hotel. Another $8. That's $28 for the day.
Multiply that day by 6, since most people stay that long, usually longer. That's $168.
Those little $2 here and there certainly add up. Is it being cheap when people take their own water bottles to refill for free at sinks or water fountains?
Also, many families take more than 4 people. When you're dealing with families, there tend to be budget constraints, and quite frankly, who wouldn't rather put a few more dollars into the souvenir budget for their kids than the food budget?!
For me it's personally not an issue. I KNOW that no matter HOW long I stay, I would drink far more than $10 worth, so the mugs pay for themselves in a day or two, and I have no problem buying a new one each trip. But I can understand why people would be upset that they bought these mugs under certain circumstances, and when those circumstances change, it's probably very annoying.
My point is that there are definitely people who give new meaning to the loosely-used term "frugal", but there are also people for whom it really is a budget issue.
On that note, when you stay at one of the on site properties, and you get a LOS pass, does that give you the permission to go back and enter the park for free any time you like? Answer that
Obviously not, HOWEVER, it seems to me that the comparison is invalid because when people were first buying these mugs, they were not sold as being mugs to be refilled for the length of stay only; they were sold as bring-these-back-each-trip-to-refill. If (and this hypothetical goes beyond ludicrous....) Disney had ever sold length of stay passes as "pay one price, and be readmitted to the parks each time you come back for no additional charge", then yes, Disney would have to honor that, and let people in.