It isn't. There is no other purchase I can think of where you have to wear a security tag AFTER you have bought an item.
Ever look at the scribbling on your airline boarding pass after you've passed through security?
Of course, you continue to confuse an electronically downloaded video with something like a leather jacket. The difference lies in the former being intellectual property in an electronic format and the latter being common tangible property. Sure, if you buy a leather jacket you have every right to resell it (you can even include the original security tag if you like.) But you can only sell that jacket once. After that, you can't resell it again since the jacket (and optional tag) is no longer in your possession. Want to sell the jacket again? You have to buy it back or buy another one.
Compare that to an electronically downloaded audio or video file. If you were so evilly inclined, you could download a hot new magic video and then turn right around and sell it to me. Then to Richard. Then to Nate. then to a thousand others. And then five years later to Ian, James, John, Paul, George and Ringo. The point being that every purchaser of intellectual property in an electronic format (even the illegal purchasers) has the potential to become a re-distributor of the property so purchased without forfeiting that property as part of the sale. In other words, every purchaser is potentially a very real threat to the original seller (them original creator/sellers seem to have this belief that only they or their officially designated licensees should be able to profit from the sale of their own intellectual/electronic property. They're funny that way.)
Even given that true 100% bulletproof copy protection is ultimately impossible (if one human is hell-bent on working around a device created by another human, it will eventually happen), I'd rather endure the minor annoyance of seeing my name emblazoned on my downloaded copy if it helps ensure that at least some of those sales that would otherwise be lost to piracy are spared for the original seller and it gives the original creator/seller the peace of mind to continue creating and selling.
I for one want to see more videos from Andi, Paul, Jason, Dan, Dave, Kevin and everyone and anyone in the magic community who can create such quality intellectual products. I do not want to see them run out of business by piracy or even the fear of piracy. Contrary to popular belief, copy protection is not designed to keep honest people honest. It's designed to keep quasi-honest people honest.
Kudos again to Paul and Jason on Volume Two. Here's to Volume Three in the near future!!!