Battery life is the main issue. Android is definitely too open source and far too often we seen sneaky app makers allowing their apps to continue running very aggressively in the background. Apps like Facebook is a good example and you can really save quite a fair chunk of battery and resources without installing it.
I feel they are trying to take a page from Apple's iOS where it can get pretty aggressive in killing apps, although Huawei seem to have overdone it.
Not true, look at Pixel line. They have smaller batteries and their devices last so much longer than phones with batteries close to double their size. It is also a lot dependant on Manufacturer optimization. Killing off apps in the background is actually very very un-needed and actually can hurt your battery more.
You are just messing with Android's system in prioritizing applications to keep alive and within memory. In fact, you want to keep them in memory so you do not have to waste and burn CPU cycles reloading everything from disk and since you force closed them Android itself might restart it back due to it's required services and your effort is wasted and it is worst now that you don't even see it in multitasking tray. Android is smart enough to handle all of this already, messing with stock settings is not the right way.
Apple in-fact does not kill an app in the background instead, their apps come to a complete stop less the services it may run for notifications. (I write apps for iOS and Android both OS does the same now) What is more impressive that it even compresses the resident memory of the app down to as low as 10MB from apps that can take up to 300-400mb when active. Then only time they kill apps is when the system really needs it but it is rare it does thanks to the compression (Some Android does not have)
The only time to force close apps when they're unresponsive.
