> On the other hand, I don't see why so many people think that battery life is so important.
Pretty simple:
1) Not everyone wants to constantly [think about] having to recharge their mobile device, or having it constantly connected. If you go hiking for a few days, you still want to be able to call 911.
2) Applications become heavier and heavier (yay all the ads, embedded browser, 3D stuff, cloud, crypto, etc). If you're on a plane and say play a game because you're bored you may end up easily using for example 40% of your total battery power.
3) The more you need to charge the phone, the quicker the battery degrades (LiOn generally keep working for 1000 recharges). Over their lifetime (that's roughly 3 years of daily recharging) the battery will degrade to less juice within a full cycle [1].
4) Batteries are not user replaceable anymore, so require a third party to perform the swap, at premium price and without full control of the user.
5) There's enough waste as it is, and having to swap phone every 2 years or so creates even more.
6) It also is quite a task deciding which phone to buy, and if you made a mistake or don't have that much money to burn you may end up with a phone not so well supported.
7) Finally, one has to swap their settings and data to their new phone. Sure, you can use clouds. They're free at the cost of your privacy...
A powerbank mitigates some of the above problems, but only so much, and they also suffer from degrading performance by age.
[1] Anecdotal example: my MBP 2010's battery had 740 cycles and is at ~88% capacity when fully charged.