Pokemon Go players have probably noticed that some very powerful new Pokemon are missing in the wild.
Players on Reddit and elsewhere have determined that several fully evolved Pokemon from the Hoenn Region are not appearing in the wild. Most of the "missing" Pokemon are third-stage evolutions, meaning that they need to evolve twice to reach their final forms, but there's also a second-stage Pokemon on the list.
When coupled with the two Pokemon that can only be caught after raids and the two Pokemon that can only be hatched from eggs, this means that thirteen of the fifty new Pokemon (or 26%) can't be found in the wild. The full list of "Gen 3" Pokemon that can't be found in the wild includes:
It's unclear why Pokemon Go chose to hold back so many Pokemon from spawning regularly. One popular theory is that they're trying to limit the impact that third-party trackers have on the game, but that doesn't make much sense as trackers can still find the first and second-stage versions of those Pokemon and collect candies quite easily.
Another possibility is that Pokemon Go is trying to pace players so that they can't grab all the new Pokemon in the first week and run out of things to strive for while waiting for the next release of new content.
Whatever the reason, this does appear to be a deliberate decision on Pokemon Go's part and not some random glitch. We'll see if this trend continues when the next wave of "Gen 3" Pokemon get released or if Pokemon Go starts phasing out older fully evolved Pokemon from spawning in the wild.