Uh, it’s mostly just a stylistic preference I have, but it’s also based on the idea that if we want traditional headline/title style (which is mostly all caps but not so for a small number of short prepositions and other helper words, such as “of,” “and,” “a,” “the,” and so on) or all-caps, or small-caps, or all-lower-case that that should be applied as a CSS style in the style sheet.
I’m open to changing the policy but I established it at RFB probably around a year ago so I’m asking you all to follow this style more for consistency’s sake than anything else.