We have quite a few trees on our property, including big oaks. Every
year we gather huge piles of leaves, like 20 cubic yards or so (wild
guess), and put them on the curb to be "vacuumed" by a giant machine.

Enormous quantity of stuff, simply enormous.

It stikes me as an awful loss of organic matter and something that
would surely lead to soil depletion. Is that correct?

If so, what would be a practical way to address it. I cannot have a
giant compost pile. What else can I do to keep the oranic matter and
yet have a good looking yard.

i