It turns out that Dan Piponi first introduced profunctors in Haskell and they've subsequently caught on - I didn't know that and it wasn't visible from the webpage I just linked to!
On Twitter Dan Piponi wrote:
> think I was the first to implement a Profunctor type class in Haskell. But I didn't anticipate how useful it'd turn out to be.
and Bartosz Milewski responded:
> Profunctors are the basis of the whole optics library in Haskell (lenses, prisms, grates, etc.). Guillaume Boisseau and @jer_gib wrote a great paper about it: [https://www.cs.ox.ac.uk/jeremy.gibbons/publications/proyo.pdf](https://www.cs.ox.ac.uk/jeremy.gibbons/publications/proyo.pdf)