As the other user said, I found them from backpacking for roughly the same reasons.

Subsequently I’ve found them to be extremely convenient whenever I travel. They fit into a vehicle cup holder, will last months with daily use, and are cheap enough that I don’t care much if I lose or abandon them. If I’m flying I can buy them at the destination. They’re lightweight, durable, disposable, and easily replacable across the US.

At home, regular life, I avoid the cost and waste with Nalgene & stainless steel. My oldest Nalgene is thirty years old, my oldest stainless steel a third generation hand-me-down that’s eighty years old. This is the way.