that's just nonsense. there are many people very concerned about performance.

i guess you are right that some do not care about constant factors, but i am very sure most do care about algorithmic complexity. and thinking about it, that's the approach you should use for anything where every last bit of performance is not utterly needed.

I'm a Haskell programmer and I care about performance. So do many others, which is why you continue to see things like Conduit and more recently Haxl.