It's not unreasonable to leave a non-negligible effort which requires a bit of expertise to a specialist service.

I find it incredible that people are willing to outsource the decision on what the kernel does on their server to a corporation.

It's a trade off. I use CFs load balancers to simplify steering to instances, but also appreciate that you get traffic filtering (even if not perfect). I think it ultimately depends on context and goals of what you're building. I wouldn't use that setup for everything, but I've found it's a healthy default for getting stuff stood up. Long-term, I think it makes a ton of sense to build up your own solutions.

If it's a big org doing the outsourcing, maybe there are people in the org who would rather not let others within the org have an accurate idea when the blocking efforts reach the point where the vast majority of desirable visitors are turned away.

Everyone else just goes along for the ride if they want to enjoy the same convenience, as long as they can stomach it.