Because Grant declared Christmas a federal holiday in 1870, before the Unites States of America became a Federalized nation.
Grant's declaration ONLY had impact on Federal citizens, and the only Federal citizens were Federal Employees and their families.
Like...Soldiers, and staff of, what would be Washington D.C. Federal Government in the following year (1871; the year D.C. was founded as such instead of a capital within a township; I'm not referring to when D.C. became the capital, but the year it annexed everything into the territory line we know today, and removed independent contracting of the township by taking the township as it's own).
It was intended to state that the residents of this Federal system (a very small percent of the nation...it's like one district of Microsoft declaring Christmas a Holiday for it's employees) would have the day off.
Instead, later, to process the New Deal of 1936, everyone was issues a Social Security Number and taxed.
The tax was to then return in social programs to help recover the welfare of the citizens of the American States.
Previously, on the US Military had service numbers, which were then replaced by the new Social Security Number when everyone received one.
This process of getting the Federal Administration involved into jurisdiction across state citizenship lines, caused the occurrence whereby everyone had to be a Federal Citizen to receive the Social Security Number.
"If you want the benefits, then you need to be in my administrative control for me to be able to give you benefits."
More or less.
Which meant, yep, everyone that had a Social Security Number also fell under Federal Law.
And one of the Federal Laws was a recognition of Christmas as a Federal Citizen holiday.
So what was, pretty much, a Military and Federal Staff holiday became an instant national Holiday.
Christmas wasn't a national Holiday in America previous to all of this.
Many people recognized Christmas, yes, and they took the day "off", just like they took Sunday's off mostly, but they didn't really force people to shut down or anything like that like occurred in some places in the late 40's and 50's.
And I'm not sure if any State previously made it a State holiday, but I kind of doubt it.
The East was too progressive, and the West didn't like government saying anything about mandates.
Perhaps in Central America, but again...that was largely plains country so declaring anything like that for central American States was like saying, "Hey, you can give yourself the day off on this day", so I doubt any central State would have either.
The South was a bit too busy in a clash of the plains life of the central American States and the progressive life of the Eastern states, and would have held it more as an expectation that you would properly recognize Christ on Christmas as is the natural Christian thing to do.
In short...no "boss" would make you really work if he was a proper southern man.
So there's your reason.
It's a Federal Holiday because of Grant, and we're all Federal Citizens because of Roosevelt.
Honestly...it was happenstance that it's a 'National Holiday'.
>Hebrew, Greek, and more similar resources on ILPSpiritual:
a set of neurological processes dealing with value placement, empathy, and sympathy through the associative truncation of relative identity, and which has reached a value set capable of being described as reverent to the individual, and from which existential experience and reflection is capable explicitly.