Disney clearly does not care about resale value. If they did, RIV (and later resorts) would not be restricted.
What's more, resale value of a timeshare is not entirely predicated on "what it is worth to own," and that's because timeshare is a product that is sold, not bought. Very few people understand the inherent value of owning one, so there are few "organic" prospective buyers. But, there are many many people own them. Some of those many many people will want to divest themselves at any particular point, and become sellers. So, even though owning has positive value, selling might not be, simply because there are not enough people who recognize the value proposition (and hence not enough prospective buyers) relative to the number of sellers in the market.
This is what makes Wyndham an incredible value purchased resale---particularly when you add in the arbitrage opportunities presented by the major exchanges.