Hierarchies are better because they form a natural hypertext.
I'm in my documents folder. I see a list of all the categories of stuff I have. Whatever I'm looking for, it's in one of them. I go into a folder, and I see all the categories in that folder and none of the stuff outside of it. I've narrowed my focus and increased my depth. I can browse.
Sure, tags are more flexible, but (1) I find I almost never actually need them, because in most cases a hierarchy is good enough, and (2) tags don't function as a hypertext and won't let me explore. A big list of tags is much harder to dig through than nested folders.
Granted, it doesn't stop at tags or hierarchy. You can use both—on top of which, there are hierarchical tags, soft links, hard links, and even textual hyperlinks. But out of all of these, I find hierarchy to be the most important one. Given the choice among all of them, I always start with hierarchy and I typically find I don't need anything else.
I'm in my documents folder. I see a list of all the categories of stuff I have. Whatever I'm looking for, it's in one of them. I go into a folder, and I see all the categories in that folder and none of the stuff outside of it. I've narrowed my focus and increased my depth. I can browse.
Sure, tags are more flexible, but (1) I find I almost never actually need them, because in most cases a hierarchy is good enough, and (2) tags don't function as a hypertext and won't let me explore. A big list of tags is much harder to dig through than nested folders.
Granted, it doesn't stop at tags or hierarchy. You can use both—on top of which, there are hierarchical tags, soft links, hard links, and even textual hyperlinks. But out of all of these, I find hierarchy to be the most important one. Given the choice among all of them, I always start with hierarchy and I typically find I don't need anything else.