Why do sequels use Roman numerals?

[superchunk]

d21lewis said:

"Porch monkey"? Silly Superchunk. Monkeys don't have porches! They live in tree-houses!

I'm against Roman numerals, too. I mean, what have the Romans ever done for anyone except give us the phrase, "When in Rome...."? I say we use hash marks.
 

That would actually be awesome!