Reach and momentum in heavy vegetation. The longest machete-style blades exist to clear tall growth like cane, reeds and thick brush in sweeping strokes, where the extra length adds tip speed and lets you work standing upright rather than bent over.
Tip speed. A longer blade traveling through the same arc moves faster at its end, which is what cuts green stems cleanly. It also means fewer strokes and less bending.
The trade is control and fatigue. Long blades are tiring and harder to place precisely, and they demand a much larger clear working area.
Nobody should be within the full arc of the blade plus your arm length, and that circle is considerably larger with a long machete. Check behind you as well as in front before every swing.
Long thin blades also flex noticeably, which changes where the tip actually goes. Take a few practice swings into open air before working near anything you care about.
Under Gear & Outdoors, with the rest of the chopping tools, because the primary purpose is clearing rather than cutting.
Steel expectations are the same as any machete: soft, tough, filed rather than stoned. See what a machete is used for.