I would disagree that we don't care, because we do! She's received for Order of the Lotus and Warden Karma, both fairly close together in terms of release. Warden being released in September of 2015. So, it's been about a year, which, is about average for a champion to not receive a skin.
Counter-point to those arguments for "we do care":
Jinx received Slayer Jinx in November 2015, which means it's been ~10 months since her last skin. This was also a 1350 RP skin. Her other skins are Mafia and Firecracker Jinx, priced 975 and 1350 RP respectively. Mafia Jinx has new particles, model, animations, new sounds and VO. Same with Firecracker minus the VO lines. Slayer Jinx also has a lot of changes, on animations, particles and sounds.
Janna's current catalogue of available skins is 975 RP Hextech Janna (model changes), 975 Frostqueen Janna (model + particle changes), 1820 RP Weathercast Janna (legendary). Tempest and Fnatic Janna are only model changes but I will charitably not count them since legacy.
Poppy has 975 RP Scarlet Hammer Poppy (model changes) and 520 RP Battle Regalia Poppy (model changes). (You could unfairly argue they have particle changes on R: those aren't particularly huge).
Lulu's catalogue includes Bittersweet and Wicked at 975 RP, with Dragon Trainer and Pool Party at 1350 RP. New models for the first set, everything new for the second set.
Karma has Sakura (520), Warden (750) and Order of the Lotus (975), of which all are model changes with Lotus Order getting the whole shebang of goodies. Her legacy skins Sun Goddess (750) and Traditional (975) are model changes with the latter including Karma's old VO.
Comparatively, Karma and Poppy have equally poor skin selection if you discount legacy skins. Include them, and Poppy ekes out a win over Karma in terms of what her skins offer.
I'm not going to argue that the skins created for Star Guardian are bad. They're not. But if you compare Karma's skin lineup to any of the four new Star Guardians, you'll see that only Karma and Poppy lack 1350 RP skins and offer a mostly vanilla skin of model changes with no further additions. Poppy has Lollipoppy and Karma has Order of the Lotus to offer some different particles, but Lulu, Janna and Jinx have received superior skins in terms of how they offer to change the playing experience for that champion.
I don't think you guys "don't care"; considering Evelynn, there's champions who have it worse in the skin department. Far worse. (Hi, Urgot. Yorick, Warwick.) However, I think fielding that argument doesn't hold water because demonstrably Karma's skins have been far less inspired and offer far fewer changes to their character fantasy than the other skins do for the champions that did get some goodies this time around.
Now, if the rumour for an Elementalist Lux ultimate skin is true, it'd mean that Lux, with her wide plethora of skins and numerous particle-changing skins, would be set for an even stronger fantasy change.
But Karma fans just don't have an immersive fantasy to indulge in for alternate interpretations of Karma. As a spiritual and religious leader, Sun Goddess Karma and Order of the Lotus Karma offer a mostly "same" take on her fantasy: in both cases she represents a faith or an order at the forefront of battle. Warden Karma offers the best departure from Karma's classic skin, whereas Sakura Karma just... feels out of place? And considering she only wears a kimono top, it doesn't even offer the fantasy the splash art promises. It's also similar in theme to Order of the Lotus Karma, which is a fan-wielding (but not really) woman with a flower theme in light garb.
In summation, I disagree with the original poster's assertion that you "really don't care", but I honestly believe you can step up the game with regards to Karma and giving her a skin that offers a markedly different approach to her character, and that offers a different gameplay experience beyond "different model."