The U.S. Department of Justice has a brochure for families of missing children that advises family members NOT to go out and search:
http://www.missingkids.com/en_US/publications/fam_surv.pdf
I have no idea whether the family is aware of this document or not, but I don't think we can judge them for not being out searching when the DoJ specifically says not to. They also suggest that parents take a 'time out' away from the investigation if they need one. Granted, DB & JI are not doing all the things that the DoJ says they should be doing (or not doing) but as far as we know they are acting on the recommendation of LE not to be out there going through the woods themselves.
This is a very interesting document, and also has some good information about rewards and why you shouldn't just put one up immediately. Interesting reading for sure!