It's a "niche" gun. It has uses, just not a whole lot of them.
It can be a range toy, just like any other gun.
It can be a "poor boy's SBR" since there is no tax stamp, and doesn't have the possession and travel limitations that NFA has.
It is compact, much more compact than a fullsize rifle, and a bit easier to maneuver in really tight spots like inside a motor vehicle than even an SBR, since the bare buffer tube is much smaller than a stock (although not shorter).
Since it is a handgun, and not a rifle, for those who feel the need to carry this kind of firepower, it can be carried under a CHP.
There is a gray area here about OAL. Once you hit 26" OAL, it can be considered a "Firearm", which is not a "Handgun". Concealing a "Firearm" makes it an AOW.
Because of its short barrel, you will have to use some kind of performance ammunition to get good terminal performance much past 100yds. Inside that, regular military ammo will do as specified.
They can be sufficiently suppressed, but you have to be careful. Many 5.56mm suppressors are not rated to be on barrels below about 12"-14" by their makers. You would have to make sure to get one that is capable of going on a really short barrel.
Barrels generally get as short as 7", going to about 12", but the 10.5" is about the best overall. The 7" can be finicky, while the 12" has gotten long enough you might as well go 16" and put a stock on it.
Yes, they are very loud. The right muzzle device does help some, at least outdoors. Indoors, suppressed is the only way to go.