Why?
Well one State legislator was looking into drafting a bill to demand from would be Presidential candidates prove their eligibility (something I support completely and cannot believe wasn't done previously) by providing the “long form”.
While he was looking into this, he discovered, much to his chagrin - that his OWN State only issues a computer generated “short form” as official proof of birth within the State.
Under the “full faith and credit clause” of the U.S. Constitution - if a State says their official document is proof of birth within that State - AND it meets the requirements set forth by Congress (and the short forms do) then all other States are obligated - under the full faith and credit clause - to recognize it as proof of birth within that State.
As such, California (for example) MUST accept a Texas “short form” as proof of birth within Texas IF that “short form” fulfills the requirements set forth by Congress AND Texas law says that it is official documentation of birth within Texas.