>>10OS infrastructure which is unfortunately written in them already.
Bullshit, you don't have to use C to interface to the OS.
Thats the weakest argument ever. All sane languages have OS interfaces.
>Idris or Agda are implemented in Haskell
Doesn't dodge the main part, Haskell is based on C/C++. The runtime is the most important part, and the Haskell GHC is written in is just using the runtime.