There are also several types of RTU's . In addition to the fairly short term 10-20 years, there are RTU's with 50 and 100 year terms. I owned a European timeshare that was RTU in perpetuity- basically works the same as deeded except the transfer is whatever the resort charges and you don't have to file it as a real estate transfer.
HGVC club like some others, has been steadily increasing mandatory transfer/activation fees. Buying a platinum week at a resort with reasonable MF's and then selling or giving away if need be would probably be easier than giving away something with only a few years left but a high transfer fee. If the value were such that the owner had to pay that (and possibly more) in order to find someone to transfer it too than he might just hold onto it and rent it out for the remaining years which would cut down on the ability to find resales