Photography can be or in many peoples experience is one of the fastest way to spend money, like it's going out of fashion. Having said that, the results that can be produced are almost beyond belief. I was never aware of such things being available in the days of 35mm, though I'm sure that many of them must have exsisted then. Probably for medical & forensic use mainly. But hey, who am I to stand in the way of progress, especially when such fantastic & phenomenal results can be produced. There are several groups on fbk. devoted to stacking & macro if you want to get an idea or three of some of the things that are possible, as well as some of Col's top flight images on here.
One of the nice features of recent Olympus mirrorless is focus bracketing to stack up to 8 images and auto merge them into a 9 th photo in camera. Usually used for macro but I have used it for outside/landscape to get foreground to horizon in focus at apertures like f2.8 below (apples to far window of house is about 20 meters). Hand held too!
Also has a conventional stacking function that will take up to 999 photos and then you download and stack them in computer.