Can someone enlighten me as to why funky chemicals are needed to break rocks?
They are not needed to break the rocks, but to dissolve the hydrocarbons. Hydrocarbons are not normally soluble in water, so you need detergents or other chemicals to form an emulsion that can be pumped to the surface. After the hydrocarbons are separated, the "funky chemicals" are mostly recycled and pumped back down the hole. But they are temporarily stored in holding ponds, which can leak if not properly sealed. Some of the chemicals also leak because of bad seals on the pumps and pipe joints. It is unlikely that there is leakage directly from the shale, so the groundwater contamination is not an inherent problem with fracking, but rather with sloppy practices and corner cutting.