I had a HP Palmtop that was greased to the skids with things like that, quite a powerful device. Even the modern iPhone doesn't quite do app switching as well, to be honest (the apps are often just reloading).
Since modern apps sort of expect not to be quit, they're generally quite bad about restoring state.
Back in the early days of iOS it wasn't such a big deal -- apps expected to be quit and were good about restoring state.
(This is a general problem with iOS itself too -- to use one salient example, pre-iOS 7, the phone was rock solid at remembering what you were listening too. Set your phone down, come back however much longer later, plug in the headsphones, hit the pause button on the headphones, whatever you were listening to starts right back up.
Post iOS 7, not a chance.
In general iOS 7 was just a dramatic downward plunge in software quality, and iOS has never recovered.
Speaking of terrible software quality, now that I've reached 4 paragraphs, it's taking Safari maybe 1 second to echo each keystroke. So maybe some sort of quadratic algorithm processing text in this input box. Good lord.)
Which is also a recent development that includes Apple's own apps, too. iOS guidelines used to explicitly state that your app must expect to be terminated, and should restore state.
Another example of this is scrolling views w/ buttons. Apple put out a whole whitepaper on how you have to take care to get this problem right: it's a subtle thing where you need to figure if the touch input is intended to be a scroll or a button tap.
But after the latest redesign (a few years ago, now) "App Store" doesn't even get this right.
Try scrolling around on the "Today" tab, picking various random points on the screen to scroll. You'll notice sometimes your scroll input is completely disregarded. Totally buggy.
That's because if your touch starts on a button, you can't scroll. The button just steals it. Apple needs to read their own whitepaper!
I don't know if it's just all the original people left or new leadership that doesn't have a feel for UI or what, but things are prettty rough.
(I'm tempted to jump ship to Android/Linux, but despite Apple falling off, I know things will actually still be worse there. Unless a miracle has occurred.)
Apple should hire me as Czar of Software Quality. ;-)
Also, I'd wonder if restarting an app wouldn't be more cpu (and thus battery) intensive than just unsuspending it.