CI and CD are different things: you can use CI without CD, e.g. when you have manual process of deployment (if CD is continuous deployment) or long waterfall-like development cycles (if CD is continuous delivery).

In highly secure environments CD may not be possible at all, because of formal processes of verification and manual processes of deployment (e.g. I once worked in a project, where deployment process involved copying build artifacts from CI server to an authorized flash drive and papers signed by customer).