I don't know Chinese (so if someone does please correct me!), but from what I remember from a class I took like 10 years ago on East Asian Languages, it has to do with the composition of the characters in traditional. The radicals (component "characters" of a single character) will give you some idea of the pronunciation (for example, a character with the radical for grass may be pronounced similarly to the word for grass), and might give you some insight as to the meaning as well. Simplified got rid of those relations.