It's important to note that these "8 years" aren't actually that in practice due to the delays. The latest generations of Pixels (starting with the 8th) have 7 years of actual security updates, which is one year less, but is proper support. Hopefully the industry trends towards that as a whole - buying devices that only get 2-3 years of updates should be a thing of the past.
>>mbanan+(OP)
Isn't that related to how expensive it is to get licenses from MTK and Qualcomm for updates? Given that Pixels run on their "own" chip, driver support is probably much easier.