I've got few thoughts 'bout that:
1. It must be bringing more money
2. Non-exclusive content ruines the model's glance of exclusivity (especially new model's)
more the model was sold non-exclusive - more surfers 've seen her - less webmasters will buy the content
3. Cotnent theft is really disturbing, especially if you sell licensed content w/ documents included
from the other side - non-exclusive content brings more profit (especially if the content provider is well-known), but it takes time
and the last one - maybe they've got too many exclusive customers to produce it non-exclusive?