They forget that leaves have a function in nature too, just like everything else.
Leaves are the perfect place for small animals to hide.
They also provide a good layer above the roots of the plants to protect them against low night temperatures. And...they're a fertiliser.
When you don't like the colour, don't like what I wrote above, consider putting them on a compost heap.
You shouldn't put too many leaves on top of each other, but you can mix tehm with sand and other items.