Well it comes down to server vs desktop‎.
Keep in mind that TUV for SL is RHEL which is meant to be a business server distro. Kstars is a great application for a desktop but has no place on a server.
Back before RHEL 6 Red Hat tried to push an "Enterprise Desktop" variant of RHEL which included a lot of Desktop applications and was missing a lot of the server applications. RHEL AS (Advanced Server) included every thin‎g from both the server and desktop variants, at the time that is was what SL was built off of. Now Red Hat doesn't push the Enterprise Desktop version as much as they use too because it never caught on as well as they hoped, furthermore they minimized what they included in it to strictly what developers asked for no more no less. As for EPEL any thing can be added assuming some one is willing to maintain the packages, and you can get a fedora project shepard (kindof like a project manager) to sign off on it.

  Original Message  
From: Alec T. Habig
Sent: Thursday, September 3, 2015 09:20
To: Efraim Yawitz
Cc: Mailing list for Scientific Linux users worldwide
Subject: Re: kstars

Efraim Yawitz writes:
> Why is kstars no longer part of Scientific Linux? I'm still using 5.4
> which has this wonderful and small planetarium program. Why was it
> removed from later versions?

doesn't directly answer your question, but I use xephem: but have had to
roll my own rpm for many releases now. Just compiling a new version now
as I use it for my intro astronomy course (for making current starfields
etc for my lectures).

Over time, non-core programs come and go from TUV repository, which
composes 99% of all the packages in SL, and which the SL maintainers
have no control. You can find many of the things you'd like in a
supplemental repository like EPEL (unfortunately, neither kstars nor
xephem): if there's a critical mass of people who want the the thing.
But sometimes you just gotta do the old fashioned thing and compile it
yourself :(

-- 
Alec Habig
University of Minnesota Duluth
Dept. of Physics and Astronomy
[log in to unmask]
http://neutrino.d.umn.edu/~habig/