"Hmmm.. in all his appearances I've seen him dressed in a regular business suit, shirt and tie, not even a kippa on his head. To the best of my knowledge, orthodox Jews are dressed, well, like orthodox Jews; with the prayer shirt, the black robe, long beard and a black hat, or indoors a kippa."

Your knowledge is flawed.  That's like asking why all Orthodox Christians don't walk around wearing their priestly atire all day long.