Cardboard mulch can be thought of as generative instead of destructive. You are recycling it into soil in the lead into gold sense of “into” rather than the trash into bag sense.

Cardboard is excellent substraight for saprophytic mushrooms, which are dominant in certain desirable types of forest soil. It’s a common trick in permaculture circles for simulating second growth forest succession without having to wait forty years (takes about six to twelve month).