@burcidi-- I'm no expert, but I think it's a little bit of both.
After the animal has been cut, all the blood has to drain out. The soaking, salting and rinsing ensures that any blood that might have remained comes out.
Jews cannot consume blood because it is believed that the blood contains the soul of the animal. That's why the poultry has to be properly cleaned during the kosher poultry processing.
I don't know anything about halal meat, so I can't comment on that. However, I have a Muslim friend who has told me that Muslims are not allowed to consume blood. It sounds like there is a lot of similarity between kosher and halal.