Android user for several years, many versions, now on 13 with a Pixel 5.

I’ve never been able to understand why when switching between apps, sometimes returning to an earlier app causes a full reload of the app - like it forgets where you were, what you were doing, and completely reloads an interface, webpage, or whatever. I get the sense it’s purging every app from RAM as soon as it thinks it can get away with that, and the result is a noticeable time and continuity penalty. What gives?!? Is there a way to fix this behavior?