DARPA works on programs that go against the established paradigm and often people who have become comfortable with one way of doing something are not asking for you to come in and change it. DARPA has worked on things un-asked-for by both the military and industry.
Three examples of this are
Drones - DARPA had a drone program, transferred it to the navy where it was discontinued, but DARPA continued to work on them until the military paradigm shifted and suddenly they were incredibly useful.
Optoelectronics - in this case it was businesses that weren’t asking for optical multiplexing. AT&T and IBM had worked on multiplexing but had budget crunches and didn’t see value in it. DARPA supported optoelectronics work from 1985->2005 (20 years!)
Personal Computers - nobody was asking for most of the pieces of the Mother of All Demos. Instead of collaborative shopping lists and voice calls, the military wanted a computer that could help commanders understand what was happening with nukes and battles.
The upshot is that you can’t apply the normal maxim of “Make something people want” to an ARPA program and seek out “customer validation.” This missing feedback loop is tricky because you do need to make something people want … eventually. Decoupling from market discipline is like cave diving.