Hello, I am Chinese. Also a cook by profession.

The coating on white rice is excess starch. For paella and risotto, that is perfectly fine, if not outright beneficial.

For Asian cuisine, loose, fluffy rice is the norm. Think rice you would get at an Indian or Chinese restaurant.

Extra starch is also detrimental to frying. Fried rice in particular is generally made with thoroughly washed rice, cooked then slightly dried out. This form of loose rice has more surface area (as opposed to a clump of rice the same weight) for absorbing flavor. Unwashed rice with the exact same method will become gummy, and the starch kind of absorbs the frying oil and burns.

Sushi rice is also thoroughly washed, unwashed sushi rice will turn into gummy, chewy sushi.