Back in the old days when we used stone knives and bear skins we didn't have these fancy schmancy text editors ad IDE's that color coded syntax.
The programmer actually had to consider the next guy that was going to come along and have to mess with his code (even though there were only like 6 of us programming back then). And well, there was this common ethic we all had back then about code that was easy to read...
Bottom line: code is easier to read with key words capitalized (along with all the other niceties of indenting and commenting, etc.)
(I wonder at times if widespread use of intelisense is going to result in programmers being conditioned to the point that they get stuck on the toilet waiting for their butts to get wiped automatically.)
I guess that qualifies for the SSC Joe Celko Memorial rant award