Fair, but if Apple can replace the battery that means that so can anyone else, so yes, I expect you'll be able to replace the battery in 15 years, assuming anyone still makes the battery you need (which would apply to an easily replaceable battery as well).

Re: passive listening, I don't know why they didn't. But I think it is fair to assume there was a real trade-off. Do you really think a smart business like Apple would make their excessively expensive headphones less functional for absolutely no reason?