When introducing a new feature there's two things we can do:
(1) We turn the feature off by default.
(2) We turn the feature on by default.
If we pick (1) then new players will not be aware of the feature and they'll likely never use it even though it can be a great feature. If we choose (2) then the best we can do is inform people they can turn it off, but everyone does get to experience it.
When adjusting a feature we have one additional option:
(3) We add a 'legacy' option where the behavior is the same as before.
If we'd choose (3) then we'd have the same issue as (1) where a lot of people would never know the full potential of a feature as it is 'hidden' in the options menu. Therefore it is again best to turn on the entire feature and inform people they can change it in their game settings with a similar rationale to (2).
Bottom line: if we'd always disable features by default then we may just as well make no more features at all as nobody gets to use them. As an example of a great feature that is turned off by default: being able to drag / drop the queue of a factory to change the order. That allows you to move an engineer to the front of the queue without wasting the queue.
edit: note that this feature can be tweaked by UI mods in the patch after this patch (3.g., 3729). That way everyone gets to define their own behavior as they see fit.