> digital 'computers' that can replicate themselves
By this definition we are just a few RepRap 3d printer revisions away from creating life.
> can you explain why that is not life?
As far as I know, the answer depends on ability of such a computer to become a competent Starfleet officer.
They included it because one of the scientific definitions of “life” and specifies the ability to reproduce.
https://en.m.wikipedia.org/wiki/Life
A RepRap wouldn’t satisfy every criteria though.
