There are good reasons to remove all this information. For example, some cameras and software store serial numbers and personal information such as the name of the owner in their files.
Furthermore, one regularly sees questions like "how can I compress my images so they don't exceed the Clubsnap gallery size limit?" or "Why does my JPEG file look so bad when I compress it to less than 100 kB". Well, there are pictures out there in the gallery where all this Exif information takes more than 50% of the file size. I'd rather use that bandwidth and storage space for the image.
I also seriously doubt one could learn a lot about technique from the Exif information. To learn, look at the composition and the lighting. Whether one used 1/400 or 1/567 second exposure time doesn't really matter, and the light will be different when you want to take a similar photo anyway.
Also note that Exif information can be misleading. When I use my external flash unit, it won't be recorded in the Exif information because the camera doesn't know about the presence of the flash. Some software may also create wrong Exif entries, and reader/display software may interpret some Exif information wrong. For example, Google's Picasa messes up royally on the frame size/crop factor, claiming my photos were taken with focal lengths of several metres.
Some motivation may lie in not wanting to further the equipment fetish of some people. I've seen cases in the gallery where people commented not on the photo, but the camera brand/model used (according to the Exif information). I think it would help to look more at the pictures, not at the equipment and process parameters used to create them.
Finally, I think one should be grateful that people are so unselfish to share their photos. If anything strikes me as selfish is to demand more, more, and more from a freebie.