The dimples allow better conductivity for water to get to the perimeter drainage or sump pump located in the lowest spot of the crawl space.
Most times, water in the crawl space gets there one of three ways: a plumbing leak, water seepage from the surrounding soil (usually after heavy rain), or condensation. Humidity condenses on cold surfaces, like ducts, and drips onto the crawl space floor.
Puddles of water in the crawl space aren’t good, but the water itself won’t ruin your home. It’s the water vapor (or moisture) that causes rot, mold, energy loss, and attracts pests. And these problems don’t just stay in your crawl space. As much as 50% of the air upstairs comes from below - this means mold spores, musty smells, and humid air that dust mites love.