[joking]

the main reason is probably that the chip is already outputting the image in a lossy format, and if you reorder the pixels you must reencode the image which means degrading the image, so it's much better to just change the exif orientation.

[lsaferite]

> the chip is already outputting the image in a lossy format

Could you explain this one?

[spider-mario]

JPEG can be rotated losslessly. `jpegtran` can do it, for example (and comes with a script called `exifautotran` to automatically normalise the orientation of a bunch of JPEG files at once).

[DidYaWipe]

Image sensors don't "output images in a lossy format" as far as I know.