Leaves are jettisoned by a tree, they fall to the ground and for eons, where composted where they fell and fed the roots /soil, providing energy to help the tree the following spring create leaves.....
The original closed loop recycling process?
Then man came along and for urban trees, either removed the leaves with a OCD like drive or cut the grass so that it no longer held leaves.
Kew gardens (Tony Kirkham) were the first in the UK (I believe) to recognise this and politely told the volunteers who arrived every autumn to rake up the leaves that new thinking was in play. They now mulch the leaves with mulching mowers (to cut them up into very small pieces) so that they are consumed by worms "overnight".
This wisdom has now spread to the main central London Parks and they appreciate how the removal of leaves, removes food for the soil and this is compounded by the years of people walking over the root system. They have now set in process aeration and leaving leaves.
So, leave leaves please.