I guess it's down to eras and what was the fashionable look of those times.
What strikes me especially is the way that the then clean cover syle has given way to things that now look much like telephone directories or corner-retailers' fly-sheets: everything crammed and cramped together as if in some desperate shout with which to arrest the casual passer-by.
I have a suspicion that it's either a reflection of falling magazine sales or, more likely, those falls are the result of poor design actually putting erstwhile subscribers off. If you open those top mags today and inspect the inner pages you'd be amazed at how cramped everything is and at the plethora of tiny images, mostly too tiny to be of any real informative value. Yes, the main fashion 'stories' are still okay as regards the space pix are allowed, but apart from the full-page ads - it's a mess of too much information. IMO, I hasten to add.
But I do feel it's all gone the way of the toilet: the impossible, cultural fantasy of more for less reigns supreme.