Why Can't R2-D2 Talk?
Is there an in-universe reason why R2-D2 and other Astromech droids can't / don't speak Galactic Basic?
In Star Wars, Astromech droids (or commonly, Astro droids), were a type of droid that served as automated mechanics, performing a variety of repair duties and often serving as adjuncts or substitutes for nav computers on smaller starships. They were also able to use the mainframe of a larger ship to their advantage. Many starfighters relied on astromech co-pilots.
It seems to me if you are building droids which are heavily dependent on verbal commands and are going to provide feedback to their masters, it would be easier if it spoke a language. Requiring a translator (C-3PO, X-Wing cockpit) or attempting to divine the melancholy whistle tones of your mechanic seems like a rather limiting feature.