I suspect it has something to do with when you started using computers. In the VT-100 and MS-DOS days, you pretty much got light text on a dark background. So when GUI environments came along, dark text on a light background became the new cool thing. That's my story, so I grew to like a light background.
I'm guessing that the majority of coders today started out on Windows. Notepad is dark on light, so that became associated with the "common" user. The first peek under the hood would have been Windows command line or Linux. I could see that a dark background would feel more 'tech'.
Alternately, the current batch of programmers grew up on the Matrix movies and associate green-on-black with leet hackerdom. At least, that's the only reason I can come up with--use a VT220 for a while and everything will look purple when you look away.
I'm guessing that the majority of coders today started out on Windows. Notepad is dark on light, so that became associated with the "common" user. The first peek under the hood would have been Windows command line or Linux. I could see that a dark background would feel more 'tech'.