It's been tried, eg. Clean, Dylan, or Miranda. Results are not really encouraging, and the language often gets open-sourced after its owner realizes they can't make money off it. And those languages are really nice languages (Dylan is my favorite Lisp variant, and Clean and Miranda are in many ways friendlier versions of Haskell).
Companies tend to have much better luck if the language is attached to a product, either as a scripting language or as part of a RAD suite. Think of AutoCad/AutoLisp, Flash/ActionScript, or Visual Basic.