Because the cost of an error in different systems is different, and it is disproportionately lower than the cost of formal verification in 99.999999999% of case

Because the cost of an error in different systems is different, and it is disproportionately lower than the cost of formal verification in 99.999999999% of cases. Where verification is needed and rational, it has long been used. Because the only thing in common between the development of intangible products (software) and the engineering of tangible products is the cost of implementation.