Why do we rake leaves out of our yards?

I thought I’d asked this before but couldn’t find it.

Last year my husband took over the raking of the leaves. Instead of bagging them up, like I did, he just piled them around the trees. About mid summer I realized that those piles of leaves had composted into dirt and we had a nice mound of dirt around the base of the trees, which needed it!
So why don’t we just leave the leaves in our yard to compost? Or rake them to areas that could use some dirt, like dips and low spots,or where tree roots are exposed?