F# is a first class citizen in Visual Studio, yet it doesn't appear to have gained much traction in 'enterprise software development'.

I'm honestly not sure why that is, but it is a completely different way of thinking to code in functional languages.

That is $BIGCORP's loss, why would I care?

Because sometimes you don't have the luxury of choosing which programming language jobs are available for.

I don't follow. The notion put forward was "hey people who like haskell, stop improving haskell and start adding visual studio support or else $BIGCORP won't use haskell". Nobody cares if $BIGCORP uses haskell, they are free to cripple themselves if they want. If $BIGCORP actually seriously wanted to use haskell, they could afford to pay someone to add visual studio support for haskell.