> How many people own a NAS, but not a PC or Mac?

That’s arguably the wrong question: I bet a lot more would own one if they could easily backup their iOS devices to it.

The number of people that would but a NAS over just spending the 5$/month for storage is well below a percent and if you combine that with the requirement of not having a PC/Mac you may well end up in the hundreds…

There aren’t that many people that are willing to own a device from a company but not trusting that company with their data

Your numbers might be right, but Apple has implemented niche features, some even requiring expensive per-device hardware, for much less than that.

Do you have an example?

All new iPhone models support native DisplayPort output via USB-C, yet I’m not sure 1% of users even have the required cable/adapter.

Some of the power amplifiers for rarely-used bands probably qualify as well (mmWave in particular).

On the software side I’d have to dig a bit, but I bet many code paths on iOS see use of less than 1% of all users.

I'm willing to bet that more people would backup their Android device if Google provided a first party tool for user friendly backups of Android devices to local computers.