The Bowie was popular as a fighting knife in an era of single-shot pistols, when one shot may not be enough and a quick strike could save your skin.
The larger hilt carried over to some of the early ones used by Southern units in the Civil War, but the preponderance of reliable revolvers, and the unweildliness of the thing when used for general camp chores saw a lessening of its popularity.
Soldiers want 'useful' things, and soon divest themselves of those items don't prove to be so.
The need for a large knife continued after the War - but in a bit smaller size, and the Bowies were scaled down somewhat, since the clip-point blade proved quite useful for a number of things, and not 'just' as a weapon.
Those are the knives seen on the belts of the drovers and soldiers and others with a need for them and not those massive varieties used by the Free Trappers of an earlier time.
Vaya,
Scouts Out!