It's been called Juneteenth for more than a century, and has been a state holiday for almost half a century.
Wouldn't it be even more ridiculous if the US federal government took an existing celebration and renamed it?
Regardless of its history I venture that 95% of the population hadn’t heard the word before 2020, so it’s not like it was in the public consciousness.
You’re right though, even if almost joined knew about it, it _did_ have a name and so def tough to change it.
Picturing a frappe and cappuccino gives you a sense for what a Frappuccino _is_. Picturing june and thirteenth/nineteenth only gives you sense for _when_ it is.
In only contend a better name would be one where the name suggests something about the content to someone hearing it for the first time.
They don’t even give you a sense for _when_ they are. Or, more accurately, they give you the _wrong_ sense for when they are by name alone.
Heck, Juneteenth is a better name, since it is not literally month+day.