I'm curious as well, since most of the programmers I've met prefers a dark theme. :)

It depends on the monitor. Some cheaper displays don't have the contrast to make light on dark work; also color bleeding...

Given a non-IPS display, my older eyes prefer dark on light, even if I think light on dark looks better. Also, light on dark is almost impossible to project for demos and presentations!

But I'm sure grandparent is just referring to the fact that light table looks different enough from the workplace norm to make it standout and his activities more known (but even visual studio has a dark mode these days).