This doesn't invalidate your point, but man it irritates me how many states have chosen to retain a noncompliant ID tier in order to avoid eating costs or raising fees. At least my state offers a full EDL so there's some added value, but it's absurd that the 'default' local ID isn't adequate for domestic air travel.
For people without a passport, it's extremely easy to have lost a birth certificate at some point over the years. And I honestly have no idea how easy or hard getting a new one issued is from some potentially far away city or town.
That's not why. States like California have dragged their feet for a decade with RealID compliance because they want to keep IDs for people in the US illegally indistinguishable from those for citizens, permanent residents, and others here legally.
Can you elaborate on this for us non-USA people?
Historically that was sort of the case. I'd argue today that we mostly rely on state-issued IDs (especially but not necessarily driver's licenses) which are now overlaid with RealID requirements.
As a practical matter it's probably indistinguishable from what a federally-issued ID would be and I'm mostly content with not adding any more layers of identity verification than are really necessary. I'd probably oppose a push for a broadly required federal ID--although I have a passport (and a global entry card).