In universe
1. Backing up what <PERSON> wrote, this was a very important meeting where absolutely nothing should go wrong or be left to chance1. Having done software writing, testing and given demos myself, I know the last thing you want is your product coping with an unrealistic variable (in this case, blank rounds), for a board level presentation. To show you the high stakes of this meeting, here's a quote from the book2
<PERSON>, a thin, hyper junior executive was even tenser than usual. Today's meeting would be an important one at OmniCon. He was sure of that. Why, the Old Man himself would be in attendance.
(Robocop, page 28, with my emphasis)
1. This was clearly a company used to live ammo, even in the boardroom. Not only would security be on hand with it, but also consider the final scene:
! <PERSON> takes a loaded gun kept in a box in the boardroom and takes the Old Man hostage.
Not to mention that the gun <PERSON> handed the unfortunate Mr <PERSON> was also loaded.
1. 861
No one considered ED-209 would actually fire in what was meant to be a routine operation:
<PERSON> put a fatherly arm around the started boy. "Mr <PERSON> will help us simulate a typical arrest and disarming procedure."
(Page 33, my emphasis.)
Out of universe
1. The whole movie, directed by the Dutch <PERSON>, was meant to be a satire on American culture. From his European perspective, so much of the movie was thus America writ large, from the crazy commercials ("You pick the heart... and remember, we care!"), to the absurd ED-209 design. In the same vain, <PERSON> wanted the boardroom scene to be over-the-top violence perhaps (my speculation) imagining the American boardroom of the future.
2. Mega-lolz: so much of this film is black humour but this scene especially ends with multiple one-liners. From the movie:
<PERSON>: "Is someone gonna call a paramedic?"
and:
<PERSON>: "I'm sure it's only a glitch, a temporary setback."
Old Man: "You call this a glitch?! We're scheduled to begin construction in six months. You're 'temporary setback' could cost us 50 million dollars in interest payments alone."
And from the book (page 36):
Paramedic: "They should have ordered mop and pails."
1. Finally, from the perspective of 1987, the far future did not have the same Health & Safety standards we might expect today!
1 Shame then that no one thought to test ED-209 in the boardroom, on carpet!
2 I know, I should get extra marks for cool at this point. 861