Why 'mvn install' war projects?

My maven project packages a war, which only gets deployed and is itself not a dependency to other projects (in other words is a final deployable).

Questions:

• is there any reason to ever run mvn install on that package, which, in addition to mvn package only puts it in the localRepository?
• Why should a final deployable be installed if nothing ever depends on it?

For a final deployable artifact indeed there may be no reason to invoke the install phase instead of the package phase: you want to build the .war file and you don't need to install it in your local repository indeed.

However, you may want as an habit to always run integration tests, if any. Looking at the default Maven lifecycle these phases happen after the packaging:

package take the compiled code and package it in its distributable format, such as a JAR.
pre-integration-test perform actions required before integration tests are executed. This may involve things such as setting up the required environment.
integration-test process and deploy the package if necessary into an environment where integration tests can be run.
post-integration-test perform actions required after integration tests have been executed. This may including cleaning up the environment.
verify run any checks to verify the package is valid and meets quality criteria.
install install the package into the local repository, for use as a dependency in other projects locally.

Hence, by invoking install you would make sure to always execute integration tests as well. Indeed a shorter invocation would be

mvn clean verify

Less popular but more effective in these cases.