Yeah that's been the leading hypothesis for a while now, but even if that's its intended purpose, I'd argue it still does more harm than good. I work in the OR, so I might be a bit biased by only ever seeing the surgical side of things, but we take appendixes out ALL THE TIME because like to inflame and rupture, which without surgical intervention means your abdominal cavity is now full of poop, and then you go septic, and then you die. Those little fuckers are SUPER dangerous.

Intestinal biome is definitely important - if it gets fucked up bad enough, some patients need a fecal transplant, which is exactly what it sounds like: they take a donor's poop and shove it up the patient's ass deep enough enough for it to pass and hopefully shed enough microcritters to seed a new biome.

...but we don't get paged a 3am to rush to the hospital to frantically set up for a fecal transplant because some dude rolled into the ER needing a poop donation. We do get get those calls when some poor bastard rolls into the ER writhing in pain because his appendix is stretched to capacity and is getting ready to pop; or has already popped and we need to flay his abdomen open to clean him out.

So yeah, I'd vote to just make them not exist. If hospitals have to take on the occasional extra fecal transplant patient, I'd call that a fair trade.