Change was hard
A fundamental idea of the agile methodology is to alleviate this and allow for flexibility and changing requirements. The software development process should ebb and flow as features are developed and requirements change. The software should adapt quickly to these changes. That is the heart and soul of the whole Agile Manifesto.
However, when the Agile Manifesto was conceived, the state of software development and software delivery technology was not flexible enough to fulfill what the manifesto was espousing. But this has changed with the advent of the SaaS (software as a service) model.
It’s all well and good to want to maximize flexibility, but for many years, software had to be delivered all at once. Multiple features had to be coordinated to be ready for a single release date. Time had to be allocated for bug fixing. The limits of the technology forced software development teams to be disciplined, rigid, and inflexible. Delivery dates had to be met, after all.And once the software was delivered, changing it meant delivering all over again. Updates were often a cumbersome and arduous process. A Windows program of any complexity could be difficult to install and configure. Delivering or upgrading software at a site with 200 computers running Windows could be a major challenge. Thus it was not done frequently, or at least not frequently enough. Often, customers had to wait for an official release to get a single bug fix.