Genuine question: why can't R2-D2 speak organic languages?

I know that the actual reason is "because it's part of the movies' charm" but I'm looking for an in-universe reason, because it's driven me nuts since I was a kid.Like, Chewie doesn't speak Basic because he physically can't, that makes sense. But droids are artificial constructions designed to be helpful, and I can't fathom a universe in which it's helpful for them to not be able to easily communicate with organics. They're already speaking a language of beeps and understand Basic, so why do they need a protocol droid or beep-fluent human to talk back instead of a chip or something? Has there ever been any explanation, even in stuff that's no longer canon, that gave a good reason why we have beeps instead of a voice chip? via /r/StarWars https://ift.tt/2D1iYBt