Loss or breakage.
I had the original AirPods and vowed to never buy them again because replacing the battery was so expensive.
Just ridiculous to throw away expensive audio equipment because battery replacement is as expensive as 50% of a new pair.
While good headphones from the 70s are still good, maybe with some foam replacements.
I love it when you see people with a tether on their airpods to prevent loss. My headphones have a special tether which means they will never need a battery replacement, or indeed a battery