Originally Posted by Marc Sabatella 
This is pretty much a holdover from the days of slow dialup Internet connections, when the small amount of extra space meant several seconds of waiting per picture. It's pretty silly today.
It still adds up. But I think the reason is more important: in a finished product like a web site, you don't want to expose technical background information. Exif can tell too much.
Of course, that isn't necessarily the case for the situation where the web site is
about the pictures, rather than about something else which there happen to be pictures of. But we're a) a minority case and b) the people who should know how to do something about it.
