Mine have never fallen out, even when running or jumping or leaning over. Do apple's wired earbuds fall out of your ears? Seems like this varies by body.
That's a good point, I hadn't researched into this and it seems like there are solutions out there for ear shapes that don't conform well to Apple headphones.
The covers are a cool idea, and I think I'll end up getting the ones that look like Bose tips.
That said, the friction that they add by being too bulky to fit in the case makes any of these half-baked at best. The case is such a core part of what differentiates AirPods. Having to keep track of and put on / take off covers all the time sort of kills the magic.
IMO it's really a problem Apple should solve, or at least accommodate as opposed to leaving up to a hacky third party solution.
https://appadvice.com/post/airpods-dont-fit/732275