That's exactly it. The lines run all over and through the slab. Again... every water line ties in through the slab at each point. The kitchen sink, the water to the fridge, the washer, the sink in the laundry room, the sink in the guest bath, each toilet, the shower, the master tub... they all are connected to the slab. It makes no sense to simply repair one spot as there will be issues in the future.