Idk. I kinda of expect that when I buy something that all the information I would need would be present. But, I guess if you like having some of the information only, then it makes sense there's no rules for sailing space ships in the space sailing book. Especially since they charge you the same for modules with half the information in them as modules that have all the information in them.
Really d&d 5e is a mid system from an increasingly mid company.