It's true; nearly all of the work we perform as a company involves another agency, which has been by design. Agencies, for the most part, "get" what we do, so it makes sense that we would prefer to work through an agency.
Also, agencies generally already have working relationships with clients and to be blunt, don't do the kind of work that we do. There are still a lot of negative connotations that go along with Negative SEO, and many agencies would just rather not be associated with that. We have worked with well over 100 marketing agencies to date, just to put things in perspective.
Generally speaking, if you are looking for "standard SEO," we wouldn't be the best fit for you. If you came to us for this, we could recommend one of the many agencies we work with.