[Haskell-cafe] Stupid question #374: why is MaybeT not in the standard library?

[Brian Hurt]

I wrote my own implementation of MaybeT (which was a usefull exercise), 
but a quick google showed:

http://www.haskell.org/haskellwiki/New_monads/MaybeT

But I'm wondering why it's not in the standard library.  The standards 
committee just hasn't gotten around to it yet?  Or was there some 
discussion of this in the past on some (public) maillist, that my 
admittedly shallow googling failed to uncover, that someone could point me 
at?

Thanks.

Brian