I bought the smallest CamelPak a few years back and wouldn't go without it.
I carry my essentials (bino, knife, food, spare compass, bullets, etc) along with water that won't slosh around.
I can stalk with it in thicker woods or swampy areas and it fits behind my "manly/broad" shoulders, as not to catch on any/most branches, etc.
I use it for bow hunting and just hang it up conveniently.