It’s hard to see, since this is just one area, and it’s all buried anyway, but there is lots and lots of conduit under the house (the grey pipes). That way you can run wires or whatever else to different locations in the house as needed in the future (for example maybe you need some super-duper fiber-optic cable to run your holographic TV in 15 years). Just feed the wire to the pipe that goes to the family room TV area, and you are done (no ripping up walls or floors). 🙂
BTW, it looks like we will be (finally) pouring the slab/foundation for the main house on Tuesday.