It’s true that bolos or machetes can finish the job in a more efficient way, and it can even cut or chop more stuff. However, a bolo can become inefficient to carry when climbing rough terrain, plus it’s heavier. Neck knives can do the job better as it’s easy to carry even when going to rough terrain, with the same sharpness as a bolo, plus it’s easier to draw out if the situation calls for it.