Clerks was shot in black and white for budgetary purposes, they just didn't have the money to film it in color.
Frances Ha was filmed digitally (Color) and in black and white, and was done in b&w to evoke reminisces of movies such as Woody Allen's Manhattan, or works by Truffaut.
I cannot find any references explaining why La Haine is in black and white, but considering that it was filmed during riots and contained other raw footage type scenes, it may have been both a budgetary and dramatic effect choice.