There are several of solid reasons to not change anything:
1. It might not be obvious that changing a setting could improve things. You need to have a solid mental model of how the specific tech works and how the setting could influence things. Casual users don't really have a model. Well, everyone has one, but for casual users it's more like a half-drawn sketch.
1. Changing a setting might break something - sometimes for good. Worse, it could break something unrelated (at least unrelated for the casual observer). Worst case scenario, it breaks something in a subtle way, that you only notice after a long time.
2. Changing a setting might break something that you can't fix on your own. Which takes us to a crucial social aspect: nobody like to feel dumb. Asking for help in many cultures and for many individuals makes them feel dumb.