Actually. the full buckhorn rear sight is there for looks.
Buckhorn sights, later known as "full buckhorn" with its tall '"horns" curving up and almost coming together at the top were a bit of a marketing gimmick waay back then, and after a few generations began falling out of favor.
You see fewer and fewer as factory sights after WW II, and eventually they went away completely, in favor of the "semi buckhorn" style, with it's smaller, lower "horns".
The semi buckhorn does the same job, just as well, and a bit better for most people. One of the complaints about the full buckhorn was that the tall horns obscured part of your target, something that could be important shooting moving game. The smaller horns of the semi buckhorn hide much less of your game, and still do their job of leading your eye to the notch.
Today, full buckhorn rear sights are a style thing. They're on some modern guns to recreate the look of the old period deer guns. If your gun is a reproduction of a classic period piece, full buckhorns may belong there for historical accuracy.
Henrys are not accurate reproductions of anything. They have a look that imitates some historical guns, but they aren't reproductions of actual historical guns.
Like the Ruger Blackhawk (my favorite SA) they generally look like an 1880s gun, but are better!