QWhy should I use keywords and not folders for organization?
AOne problem here is what you mean by “organize” – use the word “categorize” or “group” instead.

Of course folders should be organized, in the sense of not being a mess, but it’s best think of folders purely in terms of ensuring the physical safekeeping of your pictures – best use of drive space, certainty of reliable backup, ease and certainty of restoring after a catastrophe.

Keywords and not folders should be used to categorize and group your pictures.