The Two Methodologies Today
Both Waterfall and Agile are used across different organizations today.
However, the introduction of Agile stemmed from a changing technological landscape. A few years ago, Waterfall worked for most companies because features were only released on a periodic basis.
As releases became more regular for many companies working to deliver on an hourly, daily, weekly, or monthly basis instead of a yearly one, Waterfall became less practical for many people.
With the option of Agile, teams had more flexibility to quickly deliver high functioning features and answer changing customer demand.
While there has been somewhat of a shift to Agile and it leads as the primary management approach today, many people still use Waterfall for projects that clearly rely on extensive planning and static requirements or are unlikely to change.