Most photographers today have never used a square format camera in their lives. They all shoot the rectangular 35mm format DSLRs, so it is only natural they would subconsciously want to frame and crop close ups and half lengths of individuals and couples as horizontals; just like they have seen on TV and the computer monitors all their lives.
I had always hoped to see square monitors and TVs become the standard, so verticals would look just as good as horizontals. Higher costs probably made square format prohibitive. You see, when you shoot with square format, like the Hasselbladt cameras used and preferred by flim shooting pros back then; you actually have to stop and think which way you are going to crop the image before you print it; which way will actually look the best.
With an image seen side by side on both monitors; hopefully, you will eventually learn to see with your mind's eye when an image would look best framed and taken as a vertical. I see so many horizontal images online today of wedding couples and brides that should have been verticals, which would allow the photographer to zero in on the real money shot; leaving out the unneeded and many time distracting surplus of background that adds nothing to the shot. In a way it is like when a writer learns how to edit out the empty words which add nothing to the story he is telling, as he writes.
Copyright 2014 Bill Collins
quoted from: Tales of a Super Hero Pro Wedding Photographer by Bill Collins