I think that their main appeal was basically as an Anti-NFA legal loophole into the lurid world of Short-Barrel Shotguns, but once everyone who wanted one had one, and it became clear that they weren't going to be reclassified by the ATF as an SBS, that was the end of the craze.
I still have my Mossberg 590 Shockwave 12 Gauge and I still love it just as much as the day that I bought it!
It has an extremely exhilarating yet not at all painful jolt when fired and serves as my bedside Home Defense firearm which is ideal for the relatively cramped quarters that I live in.
People often make comments about them being difficult to aim and shoot accurately, but like anything else, all it really requires is the proper technique.
Also, you can still hipfire it accurately with the aid of a laser sight, even if it is more for the sake of kicks and giggles than actual combat effectiveness.
Still, I have no issue whatsoever with admitting to the fact that the main reason I wanted one was because it was cool! Not sorry, I'm a grown man and I like what I like. Heck yeah, I watch movies and I play videogames!
I feel sorry for folks who avoid buying firearms just because it pleases them and feel the need to justify every purchase they make to others, especially strangers on the internet.
I like short-barreled scatterguns, and that's the only justification a free man needs.