If you're hiking rather than backpacking, some of this makes a lot of sense based on my experience in Hawaii.

Hawaii has summer conditions, all the time. I considered folks that carried only 3 liters of water on a hike (not backpacking) of over 5 miles to be unprepared. You needed a gallon of water (minimum) to stay out all day. I've run out when I carried less on Aiea Ridge (a 12+ mile ridge hike with scrabbling). If you aren't carrying a filter or tablets, you have to carry more water to compensate for that lack in technology.

Also, weight constraints matter a lot less when I am dayhiking. In that situation, the multitool isn't a major impediment from a weight perspective. My regular sized swiss army knife (with saw and corkscrew!) has the things Allison is recommending. Heck, without a stove, tent, several days worth of food, and a sleeping bag taking a set of 7x50 binoculars wasn't a big deal if there was something I wanted to look at from on top of a ridge.

This gets back to the numerous points made earlier on: YMMV, depending on conditons, activity, acclimitization, and experience.

Allison, welcome to the free for all.