Why would I leave apps open when I'm not using them? What's the point of constantly draining the battery, and keeping your apps open when you don't need them open to begin with? If you're using certain apps constantly, and launching them constantly interrupts your workflow, then I can understand leaving them open. But if I am going to take a picture (which I might do every few days), why would I leave the camera app open 24/7 just because nothing is "misbehaving?" There's no point in leaving Instagram open 24/7... I really only use it to pass the time while waiting for an appointment, so why leave it open all the time? I can wait 4 seconds for it to launch.
That's not how it works on iOS. iOS has very aggressive power management for apps not in the foreground. Also, most apps in the history aren't even really in memory any more, only that last few that fit are--you'll notice this because if you try to swap to them quickly, they reload instead. So you're "closing" apps that aren't even open in the first place. I just bought a new iPhone two days ago, and there are even apps listed in that history that I've never opened on this phone.
Why iPhone owners should not swipe up to close apps for purposes of battery life:
https://daringfireball.net/2017/07/you_should_not_force_quit_apps