To lock you in.

It is fairly common pratice almost engineering best pratice to not put logic in CI. Just have it call out to a task runner, so you can run the same command locally for debugging etc. Think of CI more as a shell as a service, your just paying someone to enter some shell commands for you, you should be able to do exactly the same locally.

You can take this a setup furthur and use an environment manager to removing the installing of tools from CI as well for local/remote consistency and more benefits.