In some flashbacks the author of the machine was using a chat interface in his terminal. I think he decided to let it to be entirely machine so that’s why it didn’t have a “voice”
Any interface is a possible entrypoint to hack in and gain access to the machine (the government made several attempts over the course of the series, we even meet one of the hackers). Losing that chat interface was part of locking it down before handing it over to the government, so they couldn't weaponize it, and it comes back in the 5th season (not as a retcon, as circumstances within the series).