Nicholas Knight said:
Because instead of letting the user choose to see
the image by
clicking
one link, you require them to disable ALL images, then reenable ALL
images, in order to see that one image.
The precise arrangements depend on the browser design. I believe the
experience you describe pertained to some of the earlier browsers,
such as NCSA Mosaic. Good modern browsers allow a lot of fine
control.
The experience I describe pertains to Firefox, the only browser I make
meaningful use of, and which had its 1.0 release late last year.