But 3D printing is new and cool whereas filing a blank is boring and old. :P

I think a point of that method is to demonstrate that it can be done by an amateur.

If you have a skilled professional at hand that can file a blank, you might as well assume you have a skilled lockpicker at hand.

You don't need to be a professional locksmith to file down a key, come on.

Anecdotally, it happened to me once that someone forgot to leave the (only) key to a site laboratory, I had him "transmit" via fax the key, then after rummaging in a closet full of old keys I found one that had enough material, filed it down with the high-tech tools I had available (the file of a Leatherman multi-tool) and opened the lock, I cannot see how the same cannot be easily done with a 2-D print of the profile of a "virtually generated" key instead of the fax.

> can be done by an amateur

Like the Average Joe who has a 3D printer, and knows how to use it to produce something that won't break when inserted into a lock and turned.