I think I've brought this up in movepool oddities, but the fact that Kartana learns Smart Strike at all is just stupid. It has no horn to speak of, and its main gimmick is that it's really good at slashing and cutting, not stabbing.
The worst part is that there was no reason for this to be a thing. Smart Strike is the only Steel-type attack Kartana can learn, and it learns it through TM. Do you know what else was a TM in Gen 7? Steel Wing. Same base power. Trades a bit of accuracy for a chance to raise Defense. Strictly in terms of gameplay, the two are basically interchangeable. But while Smart Strike's flavor doesn't fit Kartana in the slightest, Steel Wing would have been a great fit. It's somewhat of a slash (more of a slash than Smart Strike, anyway) and it would have been a cool reference to the two most iconic things made from folded paper: airplanes and cranes.
Alternatively: Smart Strike was added as a move specifically to give Kartana a Steel move (and they inexplicably don't want to change the type/effect of Cut despite it basically being its signature move).
Kartana
does have "horns"; they're the two protrusions on top of its head. Its personality, so to speak, is modeled after samurai, and its head is made to look like an origami version of samurai helmets, which do have horns! That said, we all know Kartana rather obviously isn't attacking with its "horns" and is instead executing the move as a thrust with its blades. Sure, it can't use the move to the letter but it definitely has the spirit of it in execution.
Smart Strike being Steel in the first place is pretty weird; there's no particular association between metal and horns in Pokémon. Not that there's a lot of horn-based attacks, I suppose; there's Horn Attack and Horn Drill, Normal moves, and Megahorn, a Bug move (which is only really Bug because of Heracross, but it's ended up being a respectable coverage option for the few Pokémon that get it, so I guess it works out), and Peck, if you want to stretch it (various Pokémon with horns get it, but it's also clearly meant to be a move primarily for bird Pokémon). It's not even widely distributed to Steel types; the Steel Pokémon that aren't Kartana are:
- Aggron (makes sense)
- Excadrill (its weird head protrusion is technically a horn, I guess, given it also learns Horn Drill, but it's also heavily associated with drill moves)
- Escavalier (doesn't really have a horn anymore, though Karrablast does, and it ostensibly gets to keep Megahorn through that link, or thrusting via its lances. Notably, Karrablast does NOT get Smart Strike)
- Celesteela (fellow Steel type UB-04; no particular arguments here, though I'm not sure if I would personally call the pointy, elongated top of its head a "horn.")
- Dusk Mane Necrozma (inherited from base Necrozma, which ostensibly gets it from the sharp points on its "head.")
There are also multiple learners of the move who either have "horns by design only" that learn it (Togetic, Thundurus), or those who do not have horns but rather horn-like structures (Cloyster, Falinks, Glastrier). I momentarily forgot about Aggron and was about to bring up fellow Gen 3 Steel type
Mawile as the only Steel Pokémon to actually have any sort of "horn," though in its case they no longer look like or function like horns and it, understandably, does not get Smart Strike.
At any rate, Smart Strike is a very niche move that I don't believe really sees any play besides Kartana, as the other STAB users have better options, mostly Iron Head, and most other learners have better coverage options. While Kartana
could learn Iron Head in theory, I think the sharp, stabbing attack implied by Smart Strike, even if it doesn't actually use its "horns" for it, fits it better than the ramming attack Iron Head is.