The practical reasons are a combination of no (not low, no) demand, and the drawback of size, bulk, balance to a shotgun size cylinder.
Capacity would be 5, possibly 6 if the cylinder is bulky enough, but that width cylinder is about twice the width of a regular shotgun, or more, and the same capacity is handled by a tube magazine without the same kind of bulk in the middle of the gun as a cylinder.
Then there is also the drawback that with a revolving long gun, someone is going to put their arm infront of the flash gap. Today's revolving long guns (which, despite marketing are essentially really only novelty items) do have some kind of a shield. Old designs I have seen never did.
SO, what you wind up with is a gun with a very thick bulge in the middle, making it awkward and uncomfortable to carry one handed, that has a potentially dangerous zone (cylinder flash gap), doesn't have any capacity advantage over regular designs, and would likely cost considerably more to make.
Sure, some would buy one, just to have, but any kind of mass market appeal? No.
The Striker 12 & Streetsweeper guns were classified as Destructive Devices by our benevolent ATF, after a few years of allowing the common folk to own them without restriction. Apparently they are just too "dangerous".
They were featured by name in the 94AWB, and even more ominously, the language of that law not only named them, but also any other firearm with a mechanism "substgantially similar to" them. Considering that those guns were essentially DA revolvers in mechanism, that gave them a foot in the door, legally, to at some later time, regulate/ban DA revolvers. The fact that the anti gunners didn't capitalize on that (yet) means only that they are waiting for the right time. The groundwork has been laid.