[kemayo]

I'm fairly sure the downside is "they'd sound worse". Headphones like this are doing a lot of signal processing -- just hooking up an input directly to the driver is going to sound notably less good.

We can argue that it's a trade-off that you should be free to make for yourself... but it's very in-character for Apple to just take a strong stance on that kind of thing.

With a 20 hour battery life I'm personally okay with it. If it was more like 4-5 hours then the need for a passive mode would be more pressing.

[acdha]

Worse in this case is a complicated comparison. The computational stuff is cool and that will definitely stop working when drivers eventually rot out of support but for general audio quality these won’t be in any way comparable to a cheaper 3+ decade old set of headphones. A huge amount of the extra complexity is making up for using Bluetooth – that has advantages but it means that you have to support a protocol stack, codecs, etc. just to approach the quality that you’d get from wired headphones for $50 in the 1990s. If you really value not needing a cable or the computational features that may be worthwhile to you but it’s important to remember that a lot of the extra cost and reduced reliability and service lifetime is required by non-core functions.