Simple answer, no-one's asked for it.
Longer answer, it lacks support, it lacks documentation, it lacks
tools and it lacks a user-base (not just end users, developers too).
To be honest, apart from my last job where we had a
UUCP/Linux/PCClone combo as our mail gateway (cheap, reliable and
efficient I should add), I haven't yet seen Linux used as
'professional' platform. Lots of people *have* it (at home) and
everyone (including me) raves about how great it is, but I don't
think anyone's yet ready to use it "for real".