Doh!
Because the source page won't be there forever.
Doh! Backatcha.
your turn.
Some will but most won't.
But archiving is one of the major copyright-infringment no-nos.
It was a central point in the WaPo/LAT lawsuit against Free Republic, and it was the reason that FR had to delete all the old archives.
Most media sites charge for archive searches and free archives cut into their revenue.
And just because an article isn't archived on FR doesn't mean it isn't available.
The original thread is there with the cite and that means you can almost always go there and buy the article.