I know alot of people complain about this… but it makes so much sense…
The battery is a consumable, and with use and age.. its performance deteriorates.. it is just common sense electrical engineering to have a power management unit change the behavior of whatever device it is, to ensure the product lasts longer, or can be used in an emergency etc.
I dont hear many people complaining, or knowing that on every device… 100% and 0 % capacity bear no relation at all to whats actually left in the battery in terms of power. They are artificial limits to prolong the life of the battery since extremes of voltage, either high or low, destroy the chemistry.