To me it seems mostly a problem of unwalled garden. When Apple owns the platform from the silicon to the development environment, it's easier for them to manage power. Wintel on the other hand has so much variety all the way down the software stack and even into hardware, it is more difficult to control... x86+Linux (Lintel?) suffers the same problem.
The unwalled garden can still be made low power. Android has set an example of tackling that problem with the battery tracker, which profiles which application is chewing up battery.
For power over USB, what do you mean? My Android cell phone can power keyboards, flash drives, and the like with an OTG cable. It certainly has no fan.
Wikipedia says: "A closed platform, walled garden or closed ecosystem[1][2] is a software system where the carrier or service provider has control over applications, content, and media, and restricts convenient access to non-approved applications or content."
Google doesn't restrict access to applications or content on my Nexus 5, so how is it a walled garden?
Which may appeal to you as a developer, but from a user perspective, that isn't a good thing.
Consider this analogy: Would you buy an "open-source" deadbolt for your house? Great feature for aspiring locksmiths! But very likely not such a great feature for 99.9% of home owners.
The unwalled garden can still be made low power. Android has set an example of tackling that problem with the battery tracker, which profiles which application is chewing up battery.
For power over USB, what do you mean? My Android cell phone can power keyboards, flash drives, and the like with an OTG cable. It certainly has no fan.