It fits into a six shot Single Six and is a blistering 1600-1700fps varmint cartridge. Those are two things that no other factory revolver cartridge do.
I fail to see the point of that...yes, it makes a QUICK varmint cartridge for a revolver, but that purpose seems a little..niche...itself, IMHO. If I'm varmint hunting, I want 2200fps+ (gets there sooner, flatter), and I'd prefer a rifle for better use of optics and a more stable platform.
Also, in terms of versatility of the .32 - sure, it can shoot .32 S&W Short, Long, .32 H&R, .327 FM, and .32 ACP (though this is simply passable, not recommended and discussed in other threads), most of those calibers you simply won't find outside of a well-supplied wal-mart or a gun store. I haven't seen .32 S&W short or long for a bit, and never a box of H&R in a reputable SD load.
OTOH, the .35-series is also very versatile, have been used for years, and between .38 Short Colt, .38 Long Colt, .38 Special and .357 Mag, you're guaranteed to find a .38-something a LOT easier than a .32-something.
Did I mention I can buy a box of .38's at my local True Value?
I see the .327 FM the same as a 6.5x55 - it'll do 80% of the tricks of it's bigger brethren with 20-30% less recoil, but you're paying for it with a much smaller market, and I think this smaller market is what kills sales.