Really? Including the desktop?
Sorry if I was wrong, but I’m pretty sure I read on some mailinglist not too long ago that SLE11 didn’t offer KDE4 either.
Well, maybe it was that it doesn’t offer newer/current KDE releases, 4.3.5 is very old. (4.3.0 was released in 2009, the last bugfix update 4.3.5 followed in January 2010…)
There was some talk after SLE 12 was released for a community release
for SLE 12… maybe it’s still in the making?
Well, KDE:Frameworks5 is being built for SLE12 since a year ago.
But there are problems with too old or missing packages in SLE.
That actually also caused problems for Leap 42.1…
I am not sure if it is actually usable in SLE12, at least it’s outdated now too (the repo contains Plasma 5.3.2 and KF 5.12.0, while 5.5.1/5.17.0 are the current versions)
Well, KDE4 was not really dead yet.
But it was clear already that support would end in August 2015, that was what had been announced 2 years ago already (when 4.11 was released).
Of course not very advantageous for a fresh product that has to be supported for years to come…
And strictly speaking, Plasma5 was stable already one year ago (5.0 was released in July 2014).
13.2 (which was released around the same time as SLE12 AFAIK) did ship with Plasma 5.1.0 (as option, not as default of course)…
or maybe my deduction was right, the reason they preferred gnome was because there was no stable kde at the time?
As indicated, there were actually two “stable” KDE desktops at the time. 
But one was to die upstream soon, the other was quite new (and there were problems building it for SLE). So that probably explains the decision to not include KDE at all. But I think it was not really because of the (in)stability of Plasma5, but rather because of packaging problems (missing dependencies, the openSUSE packages were quite fresh at the time and not really well tested, …)