That's not how it works. You get asked the question again on every update, regardless of what you chose the last time.

So there are people who were opted-in that change their minds. My friends and family opt-in rate is <50%. And most of them are non-technical.

It honestly doesn’t matter. We’re talking about hundreds of millions of devices sending data in either case. A hundred million more provides no additional value.

...unless there's a correlation between opt-in choice and usage patterns.

That’s the trade off. You don’t opt-in, then you don’t get customized stuff. Shouldn’t be surprised if Apple doesn’t optimize for your usage.

Major updates are infrequent maybe once a year if you always update, it’s not pestering you. And the UI makes it very easy to skip unlike some designs.

Unless there is a flurry of network vulnerability updates, then a bespoke fork is set in the road for them.

Security/minor updates don't prompt for this AFAIK