Nonsense. I'm no apologist for any company - they should secure their software and systems. However, if you've spent any time at all paying attention to the world of software security, you'll know that there is always another bug and another exploit on any platform. It's foolish to give up your ability to control those things and blunder around mindlessly with you device set to allow interactions with devices and networks you don't choose. Knock yourself out though - I'm sure you'll get by for a while on "should."
Would you be so apologetic if this was only an Apple issue?
If you truly believe manually disabling your wifi is the sensible solution, you're too far out there and I don't think anyone here can reach you - especially since you've probably disabled wireless on your side of the moon. A device that is not actively connected to a wifi network shouldn't be blindly broadcasting all that info. Conversely at home your device should be allowed to stay connected to sync, backup, download, etc - without you needing to manually connect and disconnect. That's ridiculous. I wouldn't own a device that I lack so much confidence in that I manually disable wifi. That is NOT a solution. Might as well start recommending that people unplug their routers when not in use. Oh, and don't forget building a faraday cage into the exterior of your home.
Also, wifi actually doesn't use that much power. It actually saves energy vs LTE, for example.