Food

You dont need to, but it does have an effect on the texture of the final dish. Typically, it's done with sliced meat, not whole cuts.

Most of the people telling you not to wash chicken are sticking a whole chicken under a running faucet and splashing everywhere, which is bad. The right way to do it is just put your cut chicken into a bowl, add some water, and swirl it around with your hand. Then you can drain off the water and add your marinade or whatever. There's effectively no difference from that and just washing dishes that have touched raw chicken.

You end up with a much more tender final product.