The reason why some chefs do not wash rice is because the excess surface starch is sometimes desirable in some rice dishes.
When chefs don't wash the rice, they retain the starch, which allows the chef to achieve the rich, thick and creamy mouthfeel that specific recipes require.
Chefs don't wash to allow for creaminess in Paella and Risotto as dishes like risotto require that the starches in the rice remain, to naturally bond with the stock and risotto.
Washing the rice before cooking it, strips away the starches and makes it impossible for the chef to achieve the signature creamy consistency.
And in paella, the excess starch in the rice helps the grains of the rice to bond with the fats and broth to form a delicious, crispy caramelized layer at the bottom of the pan, which is also known as socarrat.
And certain premium Japanese short grain rice's that are labeled as musenmai are also pre-processed using specialized machinery to remove milling dust without using water, which require no rinsing prior to cooking.
You should rinse rice before cooking as rinsing the rice also helps to kick start the process of rehydration of the rice and allows the grains of the rice to start absorbing water.
Rinsing rice before cooking also helps remove any loose surface starch, dirt and debris from the processing and transport and rinsing rice is also key in achieving fluffy, separated rice grains.
Skipping the rinsing of the rice before cooking can leave a powdery coating that makes the rice clump together and turn gummy.
To rinse your rice before cooking, place the rice in a bowl and cover the rice with cold water.
Next agitate the rice by gently swishing the rice in the bowl with your hands and you will immediately see the water turn cloudy.
Next drain the rice, by carefully pouring off the cloudy water and leaving the rice behind in the bowl.
Then fill the bowl with fresh water again and repeat the process 3 times to 4 times until the water runs mostly clear.
Rinsing white rice like Jasmine, Long Grain and Basmati Rice is highly recommended to keep the grains fluffy and distinct.
And rinsing Sushi rice is also essential as rinsing the Sushi rice removes excess starch so the rice does not become overly sticky or gluey.
Although for some rice you may want to skip the rinsing, which includes for Risotto rice, Arborio/Paella rice or enriched rice.
For risotto rice, you want the excess starch to create the signature creamy texture, so you should skip the rinsing process in this case.
And similar to that of risotto, leaving the starch in for Arborio and paella helps to thicken the rice dish.
And some packaged rice's in the United States also have some vitamins sprayed on the surface, which are washed away during the rinsing process.