While I agree that a site owner may not want people to actually steal content by opening pages within frames, I will disagree in two ways:
a) A well designed site will always have the owner's data, image, etc... so as a site owner it may even be good that someone includes the site in a frame. It is a way to get more traffic.
b) There are legitimate ways to show third party's sites within another site, particularly in traffic exchanges and other online marketing resources. A site that breaks out of frames disrupts a legitimate TE operation. A traffic exchange, among other web marketing sites, may certainly use a script that stops frame breakers. btw... it is rather simple to stop the most common frame breaking script.
This is just a matter of responsibility.
I know many programmers, Internet users and experts regard online marketers as some kind of "bad guys" (to say the least) but it is still a legitimate business and a millionaire industry.
Enjoy a great day...