It's obvious that you're not an engineer. Pre-cast wall systems require a crushed stone footing for drainage. The only reason that people pour a concrete footing in conventional construction is to have something level and stable to lay block onto - or pour a wall onto. Once in place, the pre-cast system will remain stable decades longer than any block OR poured wall system. This is due to the superior drainage beneath the walls (for groundwater), as well as the high tensile strength concrete (5000 psi) which resists all water permeation.