Yup. Nalgenes and KleenKanteens are nice but heavy. Backpacking requires less robust h20 containers. There's no reason to pack around a pound of weight just to hold your water.
Metal water bottles also allow you to sterilize your water and allow hot beverages to be produced.
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If given the choice between having just one survival tool such as a metal water bottle or a knife, I might well just pick the metal water bottle.