It's been pointed out, repeatedly, that as a rule, most actors are not only massive idiots, but also tend towards being not exactly the most stable or sober people as well.
So, imagine handing a blank firing gun to a doped up Lindsay Lohan or cracked out Charlie Sheen for a safety check. Or to someone like Gwyneth "My Vagina Should Be A Scented Candle!" Paltrow, who would very likely manage to render any prop gun utterly useless in the process. Repeatedly.
That the normal Hollywood safety procedures has actually kept this group of utter idiots from fatal firearms accidents on an annual basis as they regularly point and shoot guns at each other means they are doing something right.