It's not necessary from a hygiene standpoint in developed countries, but from a culinary standpoint it can be necessary to wash depending on the dish and the type of rice. But it can also just as much be necessary not to wash for certain dishes. The powdery free starch that coats the outside of the grain can make the rice clumpier, need for, for example, risotto and paella.
Washing rice does not remove arsenic. If you want to remove arsenic, studies show you have to boil and drain it like pasta, which is what some cultures do, but others find the idea repulsive.
rice straight out of the bag isn't 'dirty'. The stuff that comes off in water is just starch i.e. rice dust from milling off the outer husk. Washing rice only really changes the texture (unwashed is a bit sticker). There's no right way here and many European recipes ( like risotto) actually need the extra starch. Anyone who criticizes this doesn't know where they're taking about.
lol whatever keeps you clean, too many people never wash their ass at all.