This article accepts a simple, obvious, and often forgotten premise: software continues to become more complex. Back in the mainframe days, manual code review was possible. That was a combination both simpler code being developed and slower change cycles. Advanced in hardware, software and user experience (UX) have massively increased both the volume and complexity of code. The web, smartphones, and other technology have both meant far more people using technology and causes a service oriented change to work to provide software updates faster.
https://www.forbes.com/sites/davidteich/2018/06/28/machine-learning-and-software-lifecycle-tools-each-must-help-the-other/#2cb1ad571189/