I don't know why the US is never serious about these things. We don't get a day off to vote, we don't get days off to get our mandatory vaccination.
But we get Juneteenth? I'm not from Texas, and where my family lived it didn't matter much that slavery was over until the 1950s. So an awkward, meaningless gesture towards black people for helping the DNC defeat Sanders is prioritized ahead of democracy and epidemic disease.