In The Secret Doctrine, H.P.B. gives some indication of the importance of symbols in raising our consciousness, as they convey something more than the obvious meaning.

A symbol is ever, to him who has eyes for it, some dimmer or clearer revelation of the God-like. Through all there glimmers something of a divine idea; nay, the highest ensign that men ever met and embraced under the Cross itself, had no meaning, save an accidental extrinsic one. (Carlyle, quoted in The Secret Doctrine, I, 303)

Next, we find that, as hinted above, symbols have more than one meaning. In fact, each symbol has seven interpretations. "Every symbol," H.P.B. declared, "must yield three fundamental truths and four implied ones, otherwise the symbol is false."

Every religious and philosophical symbol had seven meanings attached to it, each pertaining to its legitimate plane of thought, i.e., either purely metaphysical or astronomical; psychic or physiological, etc., etc. These seven meanings and their applications are hard enough to learn when taken by themselves; but the interpretation and the right comprehension of them become tenfold more puzzling, when, instead of being correlated, or made to flow consecutively out of and to follow each other, each, or any one of these meanings is accepted as the one and sole explanation of the whole symbolical idea. (S.D., II, 538)

Why, then, have students of Theosophy to bother with this difficult subject? To begin with, the language of symbols is a complete language, and we cannot understand any great Scripture unless we learn it. In the Scriptures of the world is to be found, for him who can read them with the eye of understanding, the history of nations and races, of worlds and of the Coscomos itself, in their sevenfold natures.

There are no ancient symbols, without a deep and philosophical meaning attached to them; their importance and significance increasing with their antiquity. (S.D., I, 379)

Since the symbolic formula attempts to characterize that which is above scientific reasoning, and as often far beyond our intellects, it must needs go beyond that intellect in some shape or other, or else it will fade out from human remembrance. (S.D., I, 473)

The religious and esoteric history of every nation was embedded in symbols; it was never expressed in so many words. All the thoughts and emotions, all the learning and knowledge, revealed and acquired, of the early races, found their pictorial expression in allegory and parable. (S.D., I, 307)

So we see that a study of symbology is important. Trying to extract the hidden meaning from the seemingly fantastic or nonsensical gives our minds exercise. Such exercise develops our intuition. We get a further clue to its importance in the article by Mr. Judge on "Theosophical Symbols":

In symbology the symbol is only right when it fitly represents all the ideas meant to be conveyed, and in all its parts is consistent with the whole, as well as being in conformity to tradition and he rules of the ancients. It should also when understood be of such a character that when it is looked at or thought of, with the image of it in the mind, all the ideas and doctrines it represents recur to the thinker. (The Heart Doctrine, pp. 157-58)

Every symbol—in every national religion—may be read esoterically, and the proof furnished for its being correctly read by transliterating it into its corresponding numerals and geometrical forms—by the extraordinary agreement of all—however much the glyphs and symbols may vary among themselves. For in the origin those symbols were all identical. (S.D., I, 443)