It is a question of probability and effort. My personal estimation rule for my type of projects is it takes 3 times longer from my prototype to something I‘m comfortable having others use it and another factor to get to an early resemblance of a product. A recent interview I read an AI expert said each 9 in terms of error probability is the same effort.

Most software written does not serve a serious nation level user base but caters to so a relatively small set of users. The effort spent eradicating errors needs to be justified by the effort of workarounds, remediation work and customer impact. Will not be fixed can a rationale decision.