Why can't Juries ask questions?

I'm watching 12 Angry Men.

The Jurors bring up among themselves all these questions. Arguments then ensue.

Why should Jurors not be allowed to address their questions/concerns to people who could answer them? In what ways would this harm the process?

I think we're really hesitant to do Jury Reform, and for good reason. But how many hundreds of years, with how much progress in understanding how it is that 1) people come to decisions (cognitive) and 2) how groups of people come to decisions (social psych)? And how much more complex are the methods that Jurors have to understand? And the laws?

So much has changed since last we changed. Maybe it's time to start asking these questions.

I sincerely hope someone responds, in comments or email, "we don't allow Jurors to do this because *VALID REASON HERE*."