It depends on whether the CPL test is an efficient and effective mitigation of a substantial safety risk. That's kinda the key point - the requirements should be based on data, risk assessments, causal links and cost/benefit, not intuition.
But you're being a bit naughty. The discussion was about the ATPL flight test, or lack of it. Your analogy about operating a piece of machinery without a licence test was not a valid one. The holder of an ATPL has done lots of tests, including the CPL flight test. And after they gain their ATPL they continue to do lots of tests.
If you think that the operators of the machinery called aircraft let anyone with a licence loose on them, just because they happen to have a licence, I'd suggest you think again.