Not all software has the same level of criticalness. The difference between a bug in an airplane vs one in a game or entertainment software is gigantic. Sometimes it really is more important to get the software out quicker vs it being bug free. Plus, formally provable software exists and is used in some mission critical applications including some Airbus software. It's just that it takes a lot longer to develop. These problems are more a business and process issue, as in Boeing prioritizing speed over quality.