I don't see a functional difference between a video chat and a text chat beyond the technical limitation that if a text message isn't kept for a short period of

I don't see a functional difference between a video chat and a text chat beyond the technical limitation that if a text message isn't kept for a short period of time then the recipient will likely not be able to read it. Where would you draw the line? Telling another human to deliver a verbal message only within the next 24 hours is okay. Training a parrot to do it is okay. Programming a robot to do the same is okay? Programming a computer to do that is not? Is it okay if it's a one hour delay? Four hours? Until it detects that the user has read it? Until the user manually marks it as read (does that count as explicit deletion)? If it's stored in RAM? On an HDD? On an SSD in swap? On ticker tape?