Creating Books for Musical Theater...page numbers.

[motet]

You mean a flute book should match a trumpet book page number for page number? Why would that be desirable?

I'm guessing they lack page numbers so that things could be added or omitted at the last minute for the premiere. It seems a necessary evil, not a feature that one would seek to replicate once things are finalized. I've played in operas for 40 years and can't recall a part where the pages weren't numbered.