I personally have purchased sub-primals from the display case of a couple highly reputable butcher shops and never thought once that they needed to be cleaned before bagging.
OTOH when I purchase meat in the cryovac I always take a clean cloth wetted with 91% rubbing alcohol and wipe down the exterior of the cryovac. Why? You might ask? I see
people just like me bent over the display bins sorting through all the meat available. I just wonder how many hands have handled that meat before it gets put in the bin. I’ve even seen a man sneeze over the display bin!