When looking at the aesthetic reasons to crop, Luminous Landscape has an interesting essay on the topic. HERE IS THE LINK.
In the final analysis, you must let the image and it's message tell you where to crop*, not the shape of the sensor.
When I was printing film, I cropped everything. And by that, I mean everything. I used one of these:
| Byte size: ZERO | Content warning: NOT AN IMAGE |
A Four Blade Easel, which meant that I would print only
the area where the interest was, without regard to aspect ratio. I always viewed the negative as containing the image
plus periphery. Unless I had a specific need (assignment, to fit a certain frame, etc) I don't think I EVER printed in a 3:2 aspect ratio. Or any other even numbered aspect ratio for that matter.
Now with digital, for some reason, it is SO HARD for me to crop. I don't know why. Once I open the shot in Photoshop, it seems as though every pixel is sacred. So now, it is with a conscious effort that I break free of the 3:2 boundaries.
Rad
*Now keep in mind that what an image tells you and what it tells me might be two completely different things - that's where the artist's sensabilities come in