Well, a lot of computers cost about $1000 and the depreciation schedule for computers is 5 years. Since iOS 10 won't come out until 2016 at the earliest...
That's just because an accountant somewhere decided 5 years was a reasonable average time to write down the value of the PC as an economic asset. Given both the chances of hardware failures and general accounting practices, that probably wasn't unreasonable at the time. But it doesn't mean that the value of a 5-year-old PC has suddenly become zero to a user if it's still working fine.
