A bit of an explainer on injunction scope.
In the usual case, an injunction applies only to the parties to the case: the enjoined party cannot do unto the opposing party. Most court cases only have application as between the two parties, except as one form or another of precedential value (law of the case, claim or issue preclusion, persuasive precedent, or controlling precedent) on other cases.
In a case where the government is a party, however, the injunction usually involve a determination that the government's action is invalid, and then, it's not so much the injunction, but the holding of invalidity that becomes the issue. How far does that extend?
In the usual case, a district court holding has limited precedential value: it really only controls the parties before the court, and maybe (persuasive) other courts within the district. Once it is affirmed by the court of appeals, it becomes a binding precedent in that circuit, and whatever states comprise it. And becomes not controlling precedent, but "advisory" or persuasive to courts in other circuits If ruled upon and affirmed by SCOTUS, it's nationally controlling precedent.
Which brings us back to the injunction. How far should the government be permitted to continue to enforce a law or policy that has been held invalid by only one court. Granted, that ruling in and of itself may cast the law or policy into serious doubt, but then there's Reed O'Connor.
Without extending the holding beyond the parties, you get a different ruling from every district court considering, some enjoining some not, and on differing grounds.
Once it makes it to courts of appeal, you get something like 11 variants, one for each circuit.
You avoid that "chaos" by permitting either circuit-wide effect (11 variations) or national effect (no variations).
Apart from the current crisis issues, it's an interesting question.