Hi Oldfella, good question!
Its multipurpose, and some people call it "in ground raised bed gardening". In the desert here, both the soil and the water are very high in dissolved solids and we don't get enough rain to leach it down into the subsoil. So by building raised beds in a low spot (my whole garden is in a depression) we can do deep watering to leach the soil without drowning the plants. Plus, during the monsoon season, any rainwater is collected in the depression and is forced to soak in rather than run-off. The other two nice things are it makes convenient paths to walk through, and it keeps me from compressing the tilled beds ( we have very heavy very compactable clay).
On another notes, I got the CT Broadleaf planted today. I gave the garden a nice soak with the overhead sprinkler to help the seedlings establish, but soon i'll switch over to row watering to encourage deeper roots.