Laws don't make things legal, the lack of law does. Laws make things illegal.
National IDs are the result of law. They do what they do by making things illegal. Do you really want a small piece of paper, issued by a faceless bureaucrat, adding more illegality to pretty much everything? May be good for a few cases, but ... pervasively?
I want the illegal presence of certain people made unmistakeably obvious, and therefore I want to have to prove myself a citizen.
Frequently
and
Pervasively.