No one knows, it's a secret he's never expanded on.
Because he was ahead of his time with many things that were only appreciated years after, and he probably didn't see the value in vid modes. This is pinball, and in those days vids were what was killing pinball.
They put them in to try and bridge the two, but in these days, although some are fun to play here and there, I would prefer to have them all replaced with another pinball mode of some kind. Most are the same sequence, and in home use this becomes mind numbing. When I owned BF, the vid mode basically killed that machine for me, as there were only 6 modes, and one was the same vid mode with the same obstacles played every game. I couldn't take it anymore. I used to practice with my eyes closed, but was never able to actually pull it off.