[Haskell-beginners] cabal installs parsec-2.1 not parsec-3.1? Same with QuickCheck-1.2 not 2.1?

Why is it that when I run "cabal install parsec" or "cabal upgrade parsec", it does not install the latest 3.1 version but instead sticks with the current 2.1 version? The same goes for quickcheck, where it will stay at 1.2 and not upgrade to 2.1. To install the latest versions, I need to explicitly specify the version. I thought /upgrade/ is supposed to upgrade to the latest version. Is there reasoning behind this?