Agile practices can be viewed in two ways: recipes and sensors. People with a lot of software experience wrote down the practices that made them most productive. In addition, the practices reveal the ways in which we are unproductive by amplifying the pain they cause.
Continuous delivery is both part of the agile recipe and a great revealer of inefficiencies. Moreover, in order to reap the benefits of agile, you need to be agile through all phases of the software development lifecycle. Iterative planning and development don't count for much if your user stories and bug fixes languish in a repository for weeks on end before stakeholders and customers ever get a look at them.