Comment by orbital-decay

For EVs you need at least a hoist/lifter/crane/other power tool to replace a battery. But sure, there's no actual engineering reason they can't be replaced by the user. Same for the smartwatch - you can replace a battery in most ordinary wristwatches that use them, why not the smart ones? IEMs are usually too small and that's where the engineering limitations might matter. Headphones, no problem.