Interesting observation:
I set a schedule on my router to turn off the WiFi during the day when I'm the only person here and connected via Cat6.

I know I don't have outsiders on my network.

• Network is password protected
  
• Approved devices are whitelisted by MAC address
  
• I don't broadcast the SSID, so neighbors can't even see it
  
• My property is large and the distance to my neighbors is greater than the built-in capability of a laptop or mobile device and my neighbors are too backward to have any idea how to boost/hack someone else
  
• Because I can look at the connected devices and logs

I can see a noticeable improvement to overall intra-network speed and to my internet speed.
I think just so many smart phones, tablets, AppleTV's, smart bluray, satellite box getting schedule info, and so on eat up a lot more than one expects. All these things want to get time updates, weather updates, the apps all check for new versions regularly, blah blah blah... When you put it all together on enough devices the routine overhead of just laying around is a lot more than 'idle' should be.