Mostly because if I remember correctly that unit wasn't used very often. I think they only appeared in one or two episodes of the original show, if I'm not mistaken?
It's just a somewhat obscure MS to me I suppose, which makes it interesting. XP
Never appeared in the original show. :p
Was featured in MS IGLOO; the Jotunheim was assigned to test them out, and after the tests were concluded, the remaining suits were assigned to the Jotunheim to protect it.
They were ridiculously fast, but never saw widespread use because the original production models had faulty reactors that would overload and destroy the suit if pushed anywhere near their limits.