Re: hardly anyone upgrades Android from one major version to the next using OTA updates
As an example of people not wanting to upgrade; Win 7 -> Win 8 -> Win 10 involved a lot of changes in how things work for the user.
Very good example, the main difference thought, is the ability to roll back to a previous OS.
People went back to XP when Vista was out, and then went back to Windows 7 when 8 or 10 was out.
We cannot do that with phones.