Bolsters and high-performance knives
In between the blade and the handle, there's a section on the knife that encounters a very substantial amount of stress. This section is generally where your index finger would rest when you grip the knife. Imagine all the force coming from cutting and chopping ingredients being exerted on a very small section of the knife. This is why many budget knives bend, crack, and fail at this exact section on the blade. This is why bolsters are very important.
Bolsters are pieces of softer metal, fastened on both sides of that knife section. The bolster material needs to move in a similar way to the blade steel, therefore the bolster must be made of a sturdy metal. A bolster that is not metal is not a bolster, but rather, part of the handle material. It has to be made of a sturdy metal that's tough enough to strengthen and reinforce, just like the muscles on a bone.
This is precisely why I love to use brass for most of my bolsters. It's tough and soft enough to reinforce the knife blade, and as a plus, it's self-sterilizing. A brass bolster kills off all bacteria on its surface (see the oligodynamic effect) similar to the way silver does.
Bolsters are difficult to fit and costly in time and material to make, that's why very few knives have them. Based on the experiences of my fellow knife nerds though, only the best-performing knives have them, and it's only these knives that can truly claim high-performance.