Thank you for your post!
This was an intentional change in FileMaker Pro 15. There is currently no way to revert this behavior. You might also see Behavior changes in FileMaker Pro 15.
There is also a Product Idea you can add your vote to: turning on scroll wheel navigation as an option
The complaints included damaged data and unreliable workflows that were a direct result of the previous feature set.
The change - in favor of data reliability - FIXED these problems. No; "anybody" who manages data does not share your perspective.
Providing more control in some future version would be nice.