Forests lack gardeners. In the wild, there is no one to rake fallen leaves or blow them away. Foliage falls from trees and onto the ground, where it stays as it decomposes. It is the natural process. Raking and blowing leaf litter away is unnatural. It deprives the soil and organisms that inhabit it of significant organic matter that they crave. It also interferes with insulation and moisture retention.
Of course, there are some natural processes that are not so desirable in home gardens. After all, that is why raking and blowing is standard procedure. It is not practical to leave leaf litter on lawn, ground cover, pavement or roofs. Raking and blowing removes leaf litter from where it is unwanted, or at least moves it to where it is less visible. Leaf litter seems to be so useless and unwanted.
However, other procedures are necessary to compensate for the lack of leaf litter. Mulching insulates soil, retains soil moisture, and inhibits weed growth. Watering adjusts to deficient moisture in exposed soil. Weeding eliminates weeds that germinate and grow where there is nothing to inhibit them from doing so. Herbicide may be more practical. It is all so contrary to natural processes.
It is somewhat obvious why deciduous plants defoliate through autumn and winter. They do not need their foliage as much while days are shorter and sunlight is less intense. Also, they do not want to be battered by winter wind, or collect heavy snow. Yet, their desire to mulch their own soil is not so obvious. Evergreen plants do it also. They just do it slower, and generally throughout the year.
In fact, many evergreen plants are more efficient with their mulch than most deciduous plants are. Leaf litter of eucalypti, camphor, bay and nearly all conifers actually has a preemergent herbicidal effect. It inhibits germination of seed that can reach the soil. It can be a disadvantage for wildflowers, or an advantage for weed control. Incidentally, coniferous leaf litter is likely to be combustible.
Leaf litter, composted or left to its natural processes, is natural.