HN audience doesn't represent the typical iphone user. The typical iphone user appreciates privacy but is less concerned about transmitting devices than about the phone bill. I'm sure there are people who always remember switching wifi back on (or have a true unlimited contract) but most (including me) are not part of that. I see why this feature can be viewed as critical but think it'll be an improvement for the vast majority of users.
Ideally, they would've provided a switch in the settings to allow iOS10 behaviour. Maybe they'll bring that with a later version.