For that specific customer, off the self stuff would not last more than a day or two as it had to survive -20C to 80C temperature swings in the space of a few minutes, along with the enclosure being rated to IP69K. The single board computer we used was off the shelf, then modified to survive the conditions inside the enclosure (eg: adding conformal coatings).

Making electronics survive those conditions is expensive and most people don't need that level of protection.