As hackers and engineers the idea of "creating value by doing" resonates with us. We're happy to hole up in a dark room and create. It feels great. Wish I could do that for the rest of my life.
The reality is if you're selling something then that's the only validation you should be looking at to know if you're creating value.
I say this from the perspective of starting up where the point is more easily defined as creating direct economical value.