Did the Romans not have paper of any sort? It seems odd that they only used animal skins for writing on.

My understanding is that while parchment (vellum in particular) was used in early printing press printings, such as the Gutenberg Bible, the use of paper was more common because it was so much cheaper, if less durable.

They did have papyrus but that is even less durable than paper, especially outside of very unique climates like Egypt (and the papyri that we do find there are very fragmentary). Parchment was known, but not widely used for obvious reasons.

Seems more like all this stuff is tied together in tricky ways. Why bother learning to read if the only supply of written text is people hand-writing it on fragile paper or parchment, so getting even a single page of written text is super-expensive? Why bother figuring out how to make cheap and durable paper when all text must be hand-written by the few who had time to learn how? Why bother making a way to write faster when paper is expensive and nobody knows how to read?

People need to solve all of those, and have some reason for solving each one independent of the others, before the written word can even start to proliferate widely.