In spite of sealing the "face" of the stones with newspaper, wet concrete still oozed in, sometimes obscuring as much as half of a stone's face.  Chipping eliminated this problem.

Also, judicious chipping helped highlight especially good-looking stones and gave me control over the wall's final "look".

Note the corner.  I used specially selected stones to try for a clean line running up this visually prominent feature of the house.

It's a good example of stone selection and chipping technique.