It is rare that an entity can't write requirements in such a way that no "Commercial Software" full fills them. However in most cases it is cheaper to use COTS

It is rare that an entity can't write requirements in such a way that no "Commercial Software" full fills them. However in most cases it is cheaper to use COTS software for almost everything. There are very few places in the DoD that have the core competency of writing software. Even in corporate environments how many places write their own software? Most bring in vendors for everything.