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Let's establish some common ground on our definitions. The way you stated your question makes me think your definition and ours may not be the same.
The primary grind is the grind you make that changes a blank profiled blade into a recognizable blade. This is the grind that makes the blade flat ground, or hollow ground, or saber ground (as the knife in your picture).
The secondary bevel is the grind that you use to create the cutting edge. This grind is commonly done flat as you are doing (as indicated by the sharpening jig in the picture) but can be done on a slack belt to create a convex edge as Ed described.
With those definitions in mind a blade will generally have better cutting geometry (reduced cutting resistance as Ed described) when the primary grind extends across the entire width of the blade as in a full flat grind. We may not always want the grind to be that wide and that's fine but that will come at the cost of some increased resistance.
On the secondary bevel, 25 degrees is the maximum generally used and is almost always limited to heavy chopping knives. 20 degrees (approximately) is more common on the average utility knife, hunting knife, or pocket knife. Fine edged knives like kitchen knives, fillet knives, etc might be around 15 degrees, some even finer. As Ed explained, the edge and blade design need to match the intended use of the knife.
These are just general guide lines, nothing is cast in stone....
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