Why shouldn't we? Why? Simple: because Evolution hasn't been proven yet (if ever).
You don't ask such a follow-on question until after you are sure that the thing in question is responsible for the behavior under examination...
Ok, let's replace Evolution with whatever process you claim an intelligent programmer is responsible for (change in genomes over time?). In case of a stream we look for intelligent guide to determine whether it's guided. In case of this process you state that it's guided without looking for the guide. Seems like a different standard.