At least, that what you'll hear at soil science conferences and small meetings. It's a slogan that's apt to show up in a presentation or on a sticker. It pops up in discussions among soil scientists, and we're likely to exclaim it to people in other fields at the slightest opportunity.
But for the majority of Americans, it's not really an intuitive concept. If you grew up on a farm or with a garden you'll have some familiarity with it, but growing up in Elkridge Maryland, a lovely suburb of Baltimore, I didn't really get it for a long time. I didn't see where my food came from, aside from the grocery store. I didn't see where clean water came from, aside from the tap. That's as incomplete a picture as thinking that money comes from ATMs (though as an abstract concept, money is a bit of another thing).
What it really boils down to is this: If you can't mine it, you have to grow it!
There are some abstract exceptions to this, like money and music, but all the physical stuff in our lives was either extracted from the Earth or produced on the landscape (which I would argue includes seascape, but you can make a distinction if you insist). Did you eat grains, fruits, or veggies today? They were probably grown in the soil. Even if they were grown hydroponically, the nutrients and water still ultimately cycle through the soil. Did you eat any meat? Well, that animal (or those animals, if you're enjoying crabs like a proper Marylander) traces its diet back to plants at some point. Did you have a glass of water, or perhaps 8? Much of the filtration and regulation of the water supply occurs naturally in our soils. Water treatment plants only finish the process. Once your body is finished with that food and water, where does the waste end up? Some is exhaled as carbon dioxide (soils do help regulate the atmosphere as well), but the solids and liquids end up, you guessed it, back in the soil. There, they are recycled back through this process, and it can all keep going on over and over.
These are just a few examples of the "ecosystem services" that soils provide for us, the processes that help to support our ways of life that we don't directly provide for ourselves. As our population has grown and our technologies have advanced, we have stressed these natural systems and pushed them to do more than they would on their own. We have had to learn, and are still learning, to manage and to care for (and even to create) our soils in order to continue to provide for a world full of people.
And that is why soils matter to me. Why do they matter to you?