The stupid answer is that not everything that can be automated should be.

The real answer is of a more philosophical nature, if you manually had to check A, B, C... Z, then you will have a better understanding of the state of the system you work with . If something goes wrong, at least the bits you checked can be disregarded and free you to check other factors. What if your systems correctly report a faulty issue, yet your automatic checklist doesn't catch it?

Also, this manual checklist checks the operator.

You should be automating everything you can, but much care should be put into figuring out if you can actually automate a particular thing.

Automate away the process to deploy a new version of hn, what's the worst that can happen?

But don't automate the pre flight checklist, if something goes wrong while the plane is in the air, people are going to die.

I think a less verbose version of the above is that a human can detect a fault in a sensor, while a sensor can't detect it is faulty itself.

I'm not a pilot, but my brother is, and I watched him a bunch of times go through these before takeoff and landing. I think it's about more than automation, these days the aircraft computer "walks" the pilots through the checklists but it's still their responsibility to verify each item. I think it's an interesting approach to automation, keeping humans in the loop and actually promoting responsibility and accountability, as in "who checked off on these?"

Most/all of those are individually automated.

Someone checks that they ran successfully, and vouches for it.

Automating the automation can be counter productive.

Like the release process is triggered automatically by a tag, then fails after an hour long sequence of complex steps, which forces you to re-tag, but by then your tag is out there.

Or, simply, it's a bad idea to run the entire process from scratch, but you automated it such that it's easiest, so you fix something about it and the only way to test the release process itself is to release, and you now need half a dozen releases to get it right.