Unnecessarily long disk images?

[dibdib]

I've noticed (what may be) a new trend in CD images, that once extracted from their archives they consume gigabytes of harddrive space. Is there some way to get them back down to the few megabytes that gutted disk images are supposed to be? Is there something that I haven't been informed about?

I'm struggling with space on my laptop here, and the entire point is that I 1) don't want to carry CDs/DVDs around with me just to play games, and 2) don't want to use up as much space as the installed data just to do so (every disc image I hold on here will be one more game I can't keep installed on my system. That would be stupid). I may as well just create images of my entire CDs/DVDs and store those.