[plutonic]

I really don't know, but my guess would be that in mathematics particular symbols denote particular meanings depending on the shape of / decorations on the character. Big g is different from little g which is different from bold g which is different from italic g which is different from Fraktur g. Because Fraktur g is different in meaning from just g, Fraktur gets a spot in the Unicode specs. Courier, while it is standard for screenplays, does not affect the meaning of the text of the screenplay as opposed to the use of another font.