In scouts my son’s nickname was “Jimmy Ziplock” because of his packing technique. I find zip lock type bags to be a life saver. Even though I like things organized I am not particularly gifted at achieving it, and even worse at keeping things organized. I use packing cubes some, but I really like to use ordinary zip lock type bags for many items since they can keep things clean and dry, and you can see through them.
I can see what is in them and they can keep liquids from spreading if they escape their bottles. I once had a bottle of lotion pop from the heat in the trunk of a car in New Mexico and now I always put such things into a zip lock.
I can group things, like my camera accoutrements, that go together into them and see where I put things. They are also handy for keeping electrical cords from wandering around and snagging random things. It is useful for going through airports to have all electrical stuff in one bag and all battery type things in another. It makes it easier for TSA agents if they want to look at something more closely.
I like to bring washcloths with me, they make convenient little towels or can be used to clean things or as eye compresses, zip locks are great for keeping them clean before use and containing the dirt and moisture from use afterwards.
The really big ones are useful packaging if you are out in drenching weather (for example in Japan during typhoon season). They are about the right size to use as a daypack liner. Those big ones are also useful if you are traveling somewhere with interesting fauna (creepy crawlies). We used them in rural Kenya to keep dust and bugs at bay.