Yeah, that's the answer (it's a shame it's currently so low), but I don't think it's in terms the OP will be able to relate to. I'm sure he can achieve all of those examples already.

So I'll try to refine it.

The main reason an organization uses Jenkins or Chief instead of in-house code is because they can just post job positions requiring knowledge on Jenkins or Chief, instead of minutely describing the person's tasks and training newcomers on their internal tools.

So, yeah, those tools do lots of desirable things. And slightly simplify a huge number of tasks. But the main reason one won't find a job without some experience with them is that they act a lot like competence standards on the job market.

And yeah, for a job seeker it does look a lot like they are bullshit. (And they often are - Jenkins and Chief not so much, but others are a lot.) The OP's question is a lot like "why should I learn standard calculus notation if I can calculate everything just fine on my own notation?", and if you replace that with stuff like type theory you will find people actually asking that question. The answer is always the same, it's because you need it to communicate with other people.