It's not as much of a thing in the US today, but even the European Commission has found that it's not a problem unless you're eating 5% of your bodyweight in chlorinated chicken every day. It's mostly protectionism for European poultry farmers under the guise of safety.
Sources:
European Commission. (2003, April). The evaluation of antimicrobial treatments for poultry carcasses.
European Commission. (2008, April). Environmental impact and effect on antimicrobial resistance of four substances used for the removal of microbial surface contamination of poultry carcasses
European Food Safety Authority. (2015). Risks for public health related to the presence of chlorate in food.
Yes, for tax purposes. It says nothing about the nutritional content.