Why remove your hat?

I spent some time last weekend in Santa Barabara with my Wife and her family. During one of our car rides my mother-in-law asked if anyone knew why men are supposed to take their hats off in buildings. No one knew. We discussed different places to search, and even discussed mens hat etiquette for awhile, but the conversation ended with us all acknowledging that we didn't know how this practice evolved. I spent some time searching this afternoon, and found several web sites that discussed hat etiquette, but very few that actually discussed the evolution of this practice. I did find one site, however, that offered this explanation:

The hat is removed as a sign of respect; this gesture dates back to the ancient times.  The actual point of origin is not exactly known, but the earliest stories date back to the days of chivalry. The knights would remove there helmet in the presence of the king to show that he trusted the king not to kill him and that he felt safe in his presence from any enemy. In the church, as well, a helmet would be removed as the knight felt protected in church.  It is also said a knight was always bareheaded in the presence of a lady. This is believed to be the origin for a man raising the hat from his head on the street as he addressed a woman. Today, even with a baseball cap, a man should remove it if his final destination is in the presence of women. Since then, the removal of garments of clothing in different cultures through time has been a gesture of respect in the presence of a king. This has evolved down to the removal of hats, coats, gloves, shoes, etc. to show respect for the host.