I assume the theory is that once they are on then there should need to remove them by the side of the road to fix a puncture.
I've only had one set of Marathon Plus, on my Raven about twenty years ago, fitted for a 36 mile a day commute, much of it along urban cycle paths, in the dark. They never punctured, they were replaced when the rear wore out and the commute had come to an end. I replaced them with something that rode better and it wasn't until I did so that the realisation of how much I dislike riding them really struck me, I'm scarred for life. OTOH, I regularly ride with someone who uses them for everything, day rides, touring, Audax, commuting... so opinions do differ!
Back to tight tyres, they do ease off with use and I have a feeling wired ones more so than folding. I had some rigid Marathon Racers that were a real struggle to fit, I dreaded a puncture but when the first happened, after several hundred miles, I had no problem removing or refitting. I think it's some kind of settling in, though I offer no theory about how that physically happens.