It's not about the random numbers it's about the tree of possibilities having to be defined up front (in software or hardware). That all inputs should be defined and mapped to some output and that this process is predictable and reproducible.

This makes computers incredibly good at what people are not good at -- predictably doing math correctly, following a procedure, etc.

But because all of the possibilities of the computer had to be written up as circuitry or software beforehand, it's variability of outputs is constrained to what we put into it in the first place (whether that's a seed for randomness or model weights).

You can get random numbers and feed it into the computer but we call that "fuzzing" which is a search for crashes indicating unhandled input cases and possible bugs or security issues.