The following are some of the benefits of using CI. The list is brief, and not comprehensive.
Integrating the code rarely, as seen in the Waterfall model, can lead to merge hell. It is a situation wherein teams spend weeks resolving the merge issues.
In contrast to this, integrating every single commit on your Feature branch with the Integration branch and testing it for issues (CI) allows you to find integration issues as early as possible.
Tools like Jenkins, SonarQube, Artifactory, and GitHub allow you to generate trends over a period. All of these trends can help project managers and teams to make sure the project is heading in the right direction and with the right pace.
This is the most important advantage of having a carefully implemented CI system. Any integration issue or merge issue gets caught early. The CI system has the facility to send notification as soon as the build fails.
From a technical perspective, CI helps teams work more efficiently. Projects that use CI follow an automatic and continuous approach while building, testing, and integrating their code. This results in a faster development.
Developers spend more time developing their code and zero time building, packaging, integrating, and deploying it, as everything is automated. This also helps teams that are geographically distributed to work together. With a good software configuration management process in place, people can work on widely distributed teams.
In the past, build and release activities were managed by the developers, along with the regular development work. It was followed by a trend of having separate teams that handled the build, release, and deployment activities. And it didn't stop there; this new model suffered from communication issues and a lack of coordination among developers, release engineers, and testers. However, using CI, all the build, release, and deployment work gets automated. Therefore, the development team need not worry about anything other than developing features. In most cases, even the complete testing is automated. Therefore by using a CI process, the development team can spend more time developing the code.