If the show requires serious dancing, a group should have someone on hand who can make those dances look good, preferably someone with training. You do not want dance numbers that expose your cast to ridicule or possible injury.
Choreographers design and direct the dance or stylized movement in musical productions, working closely with the director and musical director. A choreographer works with dancers to interpret and develop ideas and transform them into the finished performance.
Example: The dance requirements for Big River are simple. Even so, Doolittle is bringing in a choreographer with some dance experience -- a local dance teacher who is willing to work as a volunteer.