Rinsing sushi rice removes any excess starch, impurities and debris in the sushi rice.
The excess starch in the sushi rice can result in the sushi rice becoming, sticky, mushy and result in an overly glue like texture and cause the sushi rice to stick when cooked.
Rinsing the sushi rice and removing the excess starch in the sushi rice prevents these problems and makes the sushi rice not mushy or sticky and makes it taste better.
Sushi rice is naturally high in starch and if it's not rinsed, the excess starch basically creates a gluey film when the sushi rice cooks, which leads to a mushy and undesirable texture.
Rinsing the sushi rice also removes any dirt, dust and other small particles which may have accumulated on the sushi rice during milling and packaging.
Removing the excess starch from the sushi rice also helps the sushi rice grains cook up fluffy and distinct, instead of being clumped together.
Removing the impurities and excess starch from the sushi rice also improves the overall taste of the sushi rice and ensures a cleaner and more authentic flavor.
If you want the dish to turn out good, then rinsing the sushi rice is a must.