underground/ closed conveyor belts.

With more and more types of transport i dont understand why we dont have closed, covered belts, i know we dont see whats inside but it give us option to make them underground like pipelines. it give us some aestetic and for people with weaker computers this belts can increase performance ( less animations etc). on covers can be symbol what belt is transporting thats all. but this give us easy to make underground conveyor belt. they can use a little bit more materials and mainternance. and they exist in reality, for bulk materials it should be standard, ( open make dust and pollution on transport on long distance)

https://ideas.captain-of-industry.com/suggestions/224830/underground-pipes-and-belts-and-a-map-mod-for-it