While I understand your point, I still don't like software certifications for a couple of reasons.
Your staircase example covers one. Certifying builders is possible because we have thousands of years of experience in what makes good buildings. Also, the number of different ways to solve a given building problem are finite and well understood. Software is not in this category. Just in my career (about 2 decades), I've seen major changes in what was possible and what would qualify as good practice.
The other point is that the few certifications I have run across serve only to benefit the certifying authority. These companies sometimes appear to have no practical knowledge of the field they are certifying. This makes the certifications relatively useless.
If someone could come up with a certification that actually showed programming ability and was not just a way for a company to claim due diligence, then I would be interested. A real test of this would be if a company could be held accountable if a program failed after their certified Perl programmer refused to sign off on a design and they decided to do it anyway. If the certification doesn't provide any real teeth, what is the point?
BTW, Perl isn't an acronym.