We buy them if we are staying in a non-
DVC resort instead of a DVC for the trip (didn't have the refrigerators last time we stayed). But if we are doing DVC, we'll bring our own beverages and not get the refillable mugs. We bought them at CR on our stay there solely for the frozen Cokes. We spent a lot of time at the pool and continuously filled and refilled them on that stay. But now that they have moved the Food & Fun Center, it would be more of a hassle.
We do have a TL mug that we bring back on each trip and purchase the daily sticker when we go to a water park.