It may sound a bit ridiculous to ask whether the soil under your grass is protected from the environment. How can the sun and wind affect soil covered by turf? Well, this issue may not be quite so important for soil under grass as it is for soil in garden beds, but it still deserves your attention. Any soil exposed directly to the sun, wind, and rain is adversely affected and is under stress from that environment.
THE SIMPLE RULE IS THAT THERE SHOULD BE NO BARE SOIL ANYWHERE ON YOUR ENTIRE PROPERTY!
If the grass over your soil is not very dense, then the sun's rays can reach the dirt and dry it out. The wind then blows the dust away causing minor erosion. Similarly, rain can hit the exposed soil and cause slow but steady compaction. Look beyond your lawn to those areas under trees and shrubs growing in the yard, maybe in the turf. Is the soil under those plants bare or almost bare? If so, it is suffering from the elements. Soil under trees and shrubs should always be mulched if it is not covered by grass. Of course, growing grass under trees and shrubs is almost a hopeless task. Here again is another good reason to leave your clippings on the lawn as you mow. Those clippings serve as a mulch for the soil, protecting it from the impact of sun, wind, and rain.