I'm unfamiliar with other vacation clubs/companies, but washing Marriott/Hilton points opens you up to hundreds of resorts in every corner of the planet.
DVC is primarily focused around WDW, and really only has 3 regions: FL/SC, CA, and HI. Washing resale WDW points to use at another WDW resort really doesn't gain you much. Better to keep as is, otherwise Disney will have to turn into scummy high pressure timeshare salesmen to get the direct sales if the alternative is to simply go resale and wash.