Over at the Holy Whapping there is an excellent article by Drew on the natural Catholic sense for exotic symbolism.
I think the underlying reality is that pomp and ceremony create a sense of religiosity in mankind. The Old Testament ceremony ordained by God is a perfect example of this need. Christ did the same kind of thing. For example, when he healed a blind man, he spit in the dirt, made some mud, rubbed it on the man's eyes and said, "Be opened." He could have just simplified it and left out the POD act of make mud out of his spit. But he didn't. It reminds me of the funny, yet POD, custom in My Big Fat Greek Wedding where they spit on folks to "keep the devil away."
And let's not forget Christ's approval of the very POD act of the Magdalene pouring costly oil on him. If things are important they become ceremonial. If you get married, you dress up in a weird costume. If you go to a very nice restaurant, the waiters where costumes called "tuxedos" and wear a white napkin on their arms. Many of you will put on funny hats for New Year's and blow plastic horns. Festivities necessitate festive customs, rites, and vesture. Why would it not be so for the most important function of our existence: the Worship of Almighty God.