Because she already has K2-tier stats.
This is still true, but aside from high luck (even though Hatsushimo can theoretically get higher) she doesn't really stand out or excel in anything any more. Personally, when I started playing this game, the top three were far and away Verniy, Yukikaze and Shimakaze. Now though Yukikaze and Shimakaze both are roughly on par with Shigure, Hatsuharu or Fubuki, sort of jack of all trades, master of none. Many of the other Kai-2s out-stat them in several areas. At this point the only reason I use Yukikaze and Shimakaze is they're among my highest-level destroyers and I haven't Kai-2ed some of the others (and also I like them). As more and more of the other destroyers get Kai-2s, those two are going to fade more and more into the background IMO, so I think eventually they will get Kai-2s. They don't even really need to make major stat changes, but I could see Yukikaze Kai-2 with a little bit more torpedo power or AA or something and some newer gear and an art change.
It probably won't happen for a while though.
Start using ur BRAIN... even if they get an Update someday some other Ships will get BETTER Updades and u will start to Bitch again about Stats....
EdiT: I would rather see Mutsuki or any other DD with more worse Stats then Yukikaze to get Kai-2. Yukikaze have a Torpedo stat 89 how is that low??? okay, AA is just average but come on... that is why u have that many different DD's... for Special situations to have the right DD's or it will just boring to Sortie all the time ur 20 Yukikaze's