It's because Agile as a theory (in a vacuum) works but in practice, fails to be anything but a time sink for most development teams. Agile was supposed to help

It's because Agile as a theory (in a vacuum) works but in practice, fails to be anything but a time sink for most development teams. Agile was supposed to help teams react to change and allow for elasticity in the development process but in my experience, managers rarely allow pushing deadlines or allowing for cutting features. Agile is basically just used by managers as a way to make sure people's velocity is maximized at all times.