I'm a bit surprised Disney didn't build hotels with every room adjoining the rooms on both sides. I would think Disney would have a huge percentage of families traveling together, and much higher than industry average of clients requesting adjoining rooms. They would have had to re-engineer the basic hotel layouts most hotels use, but they tend to customize anyway.
That said, now that the hotels are built, there are less adjoining rooms than those who would like to have one. They just can't guarantee an adjoining room. I'm sure in their minds they are mitigating this by offering the DVC villas and suites at the value resorts that can hold larger families, but they feel they should be able to charge for the value this brings those families. It leaves those that cannot afford the other options out of luck.