It's really just a general trend of removing and/or hiding things that might be useful for the user to make a decision of what to do:

https://news.ycombinator.com/item?id=7677898

https://news.ycombinator.com/item?id=5968237

You're right that they're (ostensibly) placing emphasis on permissions at the moment, but I don't see that staying the same if websites start adopting and using these features in any quantity.