Strategic decisions are decisions about your future course of action. It takes future change into account: emerging competitors, trends and developments, latent customer needs. These future 'states' are complex, dynamic, and foremost uncertain.
The usual weighing of pros and cons does not suffice, because we lack the data about those pros and cons. We can only guesstimate probabilities. This is like putting together a 3 million piece puzzle, with many jigsaw pieces missing and we don't know which ones.
Our vision of the future functions as the picture on the puzzle box. Our vision is the only means we have to assess the future impact of emerging changes in our business environment.