Gimmick. I can keep a real shotgun in the bedroom and the Judge is too big for carry. I wouldn't use a .410 with 28" full choke for self defense, why would I cut the barrel off to 4" and rely on it? I mean, yeah, it'll stop an attack, but so will my .38. I can't see an advantage in the Judge, personally.
For some of us, the Judge isn't too big to carry concealed, and being able to fire .410 also adds a little more variety. However, there is indeed a 12-gauge & 00 buck in the bedroom for the uninvited guests...