Perhaps because all it takes is 1/24th of a second to make a picture? Or because once the light is on, it's too late? Or because I don't want to risk missing

Perhaps because all it takes is 1/24th of a second to make a picture? Or because once the light is on, it's too late? Or because I don't want to risk missing the light being on, just because the computer is on but I m not behind it?