Oh my! Wild-eyed dreamers, or perhaps fools who've bought the business school bilge.
I've done business cases, I've forecast demand, I've done marketing studies, ... Yes, the proposed product has to work, but after that its all informed guesswork.
I once did a little consulting job for the Nicaraguan 'phone company, questioned their forecast of revenue per line. "Pues, tiene que tener fe" Well, you have to have faith.