Youtube vs iTunes

Normally if someone uses music in a youtube video, three things happen at my end:
1. I just watch the video as normal. Maybe see a music credit.
2. The video is removed so I can’t see it at all, or the music is replaced automatically.
3. If the music is “located” somewhere else, I get a message saying “Not available in your part of the world.”

Tonight something else happened for the first time:
4. A link shows up on the bottom of the video saying “Buy this track on iTunes.”

And I bought an entire album. Yeah, the first time I’ve ever been able to buy music within two clicks of a mouse from Youtube, I did so.

Generally any time I listen to music, if there was a “buy it now” option, which will get it onto my iPod within two clicks, I’d be an easy, easy, easy target. Why doesn’t the record industry understand this?