Their numbers do look awful on paper. Battery capacities tend to be a lot lower than Android phones. OTOH, Android phones consume far more battery, so comparing raw numbers isn’t really a fair comparison.
They know however that battery failing is the first thing pushing consumers to change phone and being Apple they always have to take the most anti consumer stand possible.
Admittedly it’s a less of a problem that it used to be. Outside of the Air their batteries are still not state of the art but they look less punny than they used to.
Because your comment is entirely missing the point at the moment.
How long the battery lasts, for it’s weight, is pretty much the only point of a battery.
It’s also not cheap at all especially if you don’t pay their extortionate extended warranty fee which should be included from the start.
The spare parts are readily available through their parts portal.
And it cost less than $100 to get the battery replaced on any iPhone as far as I’m aware at an Apple Store without a warranty.