Because, as I understand it, the compression force in front of the handle generated by chopping, will be evenly distributed along the arch of a choil, rather than concentrate in a point of a square angle in a choiless blade.
But there are no square angles in the ricasso or the handle, the ricasso transition into the main grind is a smooth arch, and the ricaso to tang junction is a wide arch as well.
For the tang transision:
This image comes from DWRW
http://www.bladeforums.com/forums/s...e-CGFBM-Vs-Trail-Master?p=7968462#post7968462
For the ricasso to edge transition on the grind itself:
This is an example of a more extreme rendition of the curved transition, the basic 6 and 10 won't be as extreme if they follow the pics jerry posted, but it gives an idea of how jerry finishes off his grinds termination points. Either he uses a ball end mill or he finishes them in a way that creates a radius rather than a corner at all transition points
https://knifemods.wordpress.com/2011/06/22/busse-basic-11-knife/
If you look at jerry's images of the basic series, all of the ricasso to main grinds are the same, both on the choiled and non choiled versions. Sharper and at a much smaller radius than the basic 11, but still radiused
I pulled up some 12 broken knife images, but rather than post a series of non busse knives showing where knives normally break and potentially implying that other manufacturers are sub par (most are not, the individual breaks are just a matter of steel choil, heat treat on that model, and stress risers on that model), I'll just say that of all the knife breakages I've seen, none of them were at the ricasso to edge junction on a non-choiled knife. I've seen breakages occurring at the choil, but it's always because of stress risers and cracks being present there (sharp filing marks and ridges, or heat treat problems). Nearly all of the breakages I've seen on 'combat' knives and general purpose (non-kitchen) have been half an inch away from the ricasso to edge junction, at the tip, or at the center of percussion. That makes sense because the majority of the stress is being centered on the center of percussion or the center of curvature when prying, not on the ricasso or handle. The Knives I've seen break at the handle/tang have been because of square junctions, which busse doesn't use.
So in generally I'd say it would be an extremely rare occurrence and unlikely that any knife, especailly the basic 10, would break at the ricasso to edge junction, and that adding a choil does not add noticeable strength to the area, which receives a small percentage of the stress applied to the knife.
If you read this opinion on a forum, did they give examples of knives that had broken at the ricasso to edge junction, where they may not have with a choil? did they give a reason behind why stress would be centered on that junction enough to cause failure before it happened at the tang junction or at the center of percussion/curvature?
