I am not actually all that sure that errata is made solely to align with PFS. However PFS (for better or worse) provides a standardized gaming environment for Paizo folks to both recruit new players as well as get a general sense of what is and isn't being played or causing problems.
It's a lot harder to get data from people who play outside of that environment, and because of differences in house rules/play style/GM ability/campaigns/etc, there is no standardization to determine if something should be changed or not.
Similarly...a lot of the current issues in the game system derive from the original update from 3.5 to Pathfinder (Mythic aside). Stuff like fighter-caster diparity need addressing in the core rule book, and that is best done in a new edition, not as patches in supplemental rule books. Otherwise you risk obsoleting existing books. Stuff like Unchained can only go so far.