The soil isn't bad, as what you're seeing is the remnants, slightly trodden down, of the previous circular raised bed. The problems with the former arrangement were two-fold.
First, there's the slope. Numbering the photos in the two posts 1-5, photo one which shows the site has the edge of the lawn in the foreground. This is actually about 6 inches above the bare earth, due to the downward slope in that direction. The slope continues, and the ground level at the fence is another 6 or so inches down. Knowing that, you can just about see the slope in photo 3. That means that keeping the soil raised is a problem, with rain washing it down, or just general wear and tear. Again in photo 3, on the extreme right hand side, you can see a brick wall underneath the fence. None of this brickwork is above ground on the other side, as the land is sloping up, The brickwork is actually higher as you move to the west (the raised beds being on the east side).
Our drive is higher than next doors on that side, by about two feet at the house end. That's an indication of the way the land goes. In their garden, they have a number of buildings and the concrete bases were protected by a low brick wall on our side because of soil drifting in. We had the same problem on the other side, until the fence was renewed and next door used concrete blocks at the base to adjust for the height difference. About two feet, before the fence starts, rather like our far fence, although by the time we reach the south west corner, our wall is more like three feet high.
Secondly, the soil you're seeing is additions to the ground. We might have almost a foot of soil at the north end of the garden (next to the house) but at the south (far) end it's more like a couple of inches above the chalk. Dig down, and there isn't much soil, which, apart from the general advantages and trendyness of raised beds, is a good reason for using them.
In brief - to ensure a reasonable depth of soil which won't be washed down out of the bed.
And as a matter of interest - half of the shallow bed has now been planted by Sue (who is the gardener, not me) using compost from the bin, some bags of compost bought a day of so ago when garden centres opened, and some plants bought at the same time - seeds not being available at the right time for her normal grow from seeds strategy.