You could definitely be right about them turning into kind of a fad and the necessity being inflated a bit. One potential advantage I see is having one on a magnum for recoil reduction. Still waiting to see good evidence on their effectiveness versus just adding a pound to your rifle or a muzzle brake?
I "think" the effect, even on heavy mags, as a recoil reduction device is minimal to non-existent. Surely, if anyone could prove a real reduction in recoil, then they'd be marketed as "sliced bread".
A quality brake is great for the range and repeated shooting. I know some of the more modern designs claim to have vastly improved the deafening report of early models, but I just don't find a need for them, personally, in the field. Maybe if I was long range varmint hunting and wanted to try and watch my bullet, but I don't.
I'm not even sure "fad" is the right word--I guess time will tell. For sure, they are here for now. Never thought I would see them take hold on hunting rifles (particularly bolt guns) like they have. Maybe I'm just old fashioned, but I just don't see a real need for it, myself.
I also don't really "get" the hunting use from another perspective. Anyone that has a can knows the absolute best effect is with subsonic ammo. A 9mm can with some correctly loaded subsonic ammo can be shockingly quiet. Most (if not all) truly big game hunting rounds fired from a bolt rifle will be nowhere near subsonic nor should they be for bullet performance. The sound of the bullet crack is still quite loud. It's not like you are "silent running". The first time I shot my .22 suppressor it was with high velocity ammo. I thought it was "broken". Took me about 5 mins to realize I needed to switch to std velocity ammo--problem solved.
I do agree, however, that if you are going to use one, "purpose built" usually is going to produce a better result. Kind of like using a Leatherman for any real "work". You might be able to, but usually not super efficiently. I have seen some modular units of late that look to be interesting, but more for configuring the can than using across a wide range of calibers.