After Skarner, Rumble, and Wukong were successively given new skins, the “1000 Days” group of League of Legends (including champions that have gone 1000 days without a skin) was temporarily absent for a short period. However, in mid-June, another “unfortunate” name officially became the latest member and also the only name to return to this “neglected” group. Surprisingly, it is Kayn.
Originally, Kayn was supposed to be a champion that meets all the criteria to be given a plethora of skins by Riot Games: a cool backstory, a human-type champion, and importantly, he is very “eye-catching” in the eyes of female gamers. But unfortunately, this half-human, half-Darkin champion has a critical flaw: his skill set is too complex to design effects for.

Since his release in 2017, Kayn has only been given two skins: Soul Hunter Kayn and Void Assassin Kayn. Among these, Soul Hunter Kayn is the skin that came with his champion launch. Void Assassin Kayn is the second and also the last skin Kayn has, which was released back in September 2018.
If we follow the spotlight of the skins that Kayn possesses, we will see they all have many complex effects, as in reality, Kayn has up to 12 distinct skill effects, along with 3 forms in his default, assassin, and Darkin forms.
Therefore, creating a skin for this champion takes as much effort as making 3 skins for regular champions, and that is precisely why Kayn has not been favored by Riot Games, even to the point of being outright neglected in terms of new skin releases, despite being labeled as “handsome.”

Not to mention, the effort and resources spent are one thing, but the revenue generated by Kayn’s skins probably cannot compare to champions like Zed, Yasuo, Lee Sin, or Riven. Essentially, this champion has been absent from the professional scene for most of the time since his release.
In solo queue, Kayn is only favored by one-champ players, as his playstyle does not merely exhibit skill but also requires users to master movement tricks and jungle paths to effectively utilize his champion’s qualities. Thus, Kayn has never been a hot champion throughout the 4 years since his release, and that is why he has been virtually overlooked by Riot in their “beautification” plans for League of Legends.