High frequency trading is far from the only pointless activity software and hardware developers are employed to do. At least in that realm they are pushing the state of the art, unlike presenting ads or yet another crud app.
You do realise that Jane Street (one of the big HFT market makers) publishes basically all their technical work and contributes to massive amounts of open source software? They are to my knowledge one of the main contributors to the OCaml ecosystem as well.
