I don't like doing that for personal work, but commercially it does often do the job. Image Masking / Cropping If you have an image for which you would like to only engrave a portion of that image, you can use the Image Mask feature to mask off the area of the image to be engraved. Often when I do need to do something like that with the Dslr, I will shoot more loosely-lots of room around the subject-so that I can adjust the crop later. I don't know if that is what you are seeing or if the photographers are actually shooting to the square.
They are not as connected to the frame as the photographer and will have no issue cropping to a trendy or required format. Magazines do often crop the photographer's work to meet their needs.
Being able to see with and adapt to your format is an important part of the skill of photography, so this is certainly more of an anomaly! (although I do have friends who have always cropped with their Hasselblad V cameras, I only use it, for personal work, when I want the square format) In commercial you often need to leave "bleed" room for print work and I even ended up masking my cameras for that when it was required. From the menu that appears, select Aspect Ratio, then click the ratio that you want. Click Picture Tools > Format, and in the Size group, click the arrow under Crop. I do have a grid screen in my dslr which can help when I need to crop for a client, but it isn't the same as masking the viewfinder or using the format required. Use Insert > Picture to add the image to an Office file (such as a Word document, PowerPoint presentation, or an Excel workbook). I think it does take a lot of practice either way.
I am working on a series that uses a square format and when I try to use a different camera, I always like the rectangular image better than the square crop.
Finally, download circle cropped image and crop more on turn square. Also, you can set custom image name, image extension, etc. Adjust the width, height, rotate, zoom in, zoom out, reset, clear, etc. Now, crop image using the circle crop box as size you want. I think because I have trained myself in this way, I do find it terribly difficult to shoot a square when I have a rectangular viewfinder. Select image that you want to crop in circle on turn square image into circle tool. The exception is with commercial work, where I always have masked the viewfinder to the required format (generally use LF and MF cameras).
When I have cropped, it was because I did see that crop when I shot an image and knew I would do so when I processed it. I have shot with various formats, square to long rectangles, and rarely ever crop but tend to use the entire frame.