From a business point if view the current model for disposing if vehicles is the most cost effective.
Motability saves a ton of cash by just getting the cars picked up by the Auction house transporter, and sold through auction. No doubt they will have a oarkers book and have a reserve set for the vehicles.
Compare that to having to have a staffed department to organise pick up, storage, valeting and then try and sell them like joe bloggs garage. Its not cost effective.
They want to save cash by minimising servicing and tyres. Thats why it takes a couple of hours before work is approved. My last car, the servicing was videoed for Motability, probably because it needed a suspension arm.
Motability just want the 3 year old vehicles passed on.