Except the appendix is an important organ. It has a high concentration of immune tissue and supports the immune system in the gut, and it's also a "safe house" for beneficial bacteria in the case of food poisoning or other gut "clearing" events.
It absolutely should not be just nipped out proactively.
Those are all true. However, appendicitis is still the most common abdominal surgery worldwide[0] and lots of people still die of it. It's easy to make the case that someone already undergoing abdominal surgery where the surgeon has ready access to it could have long-term lower health risk by removing it.
If you live in a country with excellent healthcare and you're never far from a hospital, the calculus is a bit different. You'll probably be fine. If you regularly find yourself far away from modern medical clinics, it's easier to defend the idea.
I had appendicitis as a kid. If you've never experienced it, trust me, you don't want it.
If you practice good food safety and hygiene (and live around people who do the same) then removing the appendix during unrelated surgeries or even preemptively before long stays at a place without emergency healthcare can be beneficial.
It's a bit of a Chesterton's Fence situation: the appendix is really useful, but for you and me the benefit was much larger 300 years ago than it is today. Today the benefit is small enough that you can remove it with only minor considerations (like being more cautious about your gut microbiome, and having a slightly worse immune system)
Makes me wonder what we'd uncover with systematic longitudinal studies (within the same culture, rather than comparing populations with distinct cultures and genetic bases) on effects of male genital mutilation.
It absolutely should not be just nipped out proactively.