Keep in mind that the points charts are not set in stone. Disney can (and, per the membership agreement, *MUST*) balance demand throughout the year. They should be pricing their seasons so rooms are equally easy/hard to get at 7 months in October as they are in July.
The fall is severely under-priced in terms of points-per-night right now.
If you are making purchase decisions based of what Disney might do, that is a huge gamble. BWV has been open for 25 years at this point, and F&W has been going on with something close to its "all Fall all the time" season for 20. Yet the BWV/BCV F&W problem has not been addressed at all until this last release of charts - and then wasn't sufficient to change patterns. Had you bought in 2004 with "Disney is sure to change those charts for availability reasons," you'd have had a lot of years of chasing very few rooms.
In the meantime, something we know Disney has done is build more resorts. That means every year there are more people looking to book into "not their home resort" since - as you pointed out, most people do want to sleep somewhere else from time to time. There is only so much property that is in highly desirable locations - walking distance to a park, on a monorail - and most of that property has been built up. Add in that much of that property was built up with lower point charts, which increases the demand for those resorts further.
And, then there are the resale buyers. You would have to believe your fellow owners are stupid to be paying BCV resale prices so they can stay out at OKW or VAKL. You only pay those prices if you will be booking the majority of your stays within your home resort window at your home resort. So each year there are slightly fewer BCV rooms available at seven months as more home resort owners snap them up.