Because there is no natural process known to science that creates coded information.
You asked where it came from, not for details of the process that lead to it getting there. You should be more specific. Anyway, the answer to the question:
by what process did information in the environment come to be represented in a nucelic acid?
Would be "I don't know, I wasn't there. There are some interesting ideas hypothesized by scientists that can achieve this goal, and some testing has occurred and some ideas remain unfalsified. Maybe it's one of them, or something like them. In general terms, and as I pointed out in
Message 41: Work was done to achieve this end."