Why YSK: I’ve been seeing an increasing number of phone photos shared online in 9:16, 9:21 or similarly tall aspect ratios, often with parts of the subject cut off. I’ve asked a few people why they cropped their images that way, and none of them knew they were cropped.
But you can still just crop it after taking the picture? 4:3 would just give you more freedom of where the cut is made for photos that might not be lined up perfectly when taken in 16:9.