Sometimes when you begin a new therapy you feel more enthusiastic - i know when i began DBT i worked very hard and was determined to get as much out of it as possible. I still do homework and contribute to the group etc but i think people do become disillusioned with therapy - add to that the personal problems people may be experiencing anyway or the fact that their finding a particular module very difficult and its easy to see how some people seem disinterested but in my view if they didn't want to DBT - they wouldn't be. Just my thoughts.