Washing your meat before you cook its is a handed down tradition some families have. These people who do this are so goddamm adamant, they will completely going into rage if you ask them not to do it. It's some compulsory thing in their head. Like the monkeys who was their sweet potatoes in the mangrove swamps before they eat them. No real reason to, they just saw another monkey do it.

I've been cooking food for a living for 20 years and there's absolutely zero reasons you should rinse the meat off. And there's actually reasons you SHOULDNT rinse it. But for asthetic reasons.