As already pointed out, there is only so much we can explain in the briefing and lets face it, how many passengers actually listen anyway?
I find that a strange statement.
If condensation is billowing out of the vents, which I have seen, then I don't think it is asking too much to make a short announcement.
Sadly, the only times are have heard this were from pilots (one a Jetset cpt)
Just seems like a no brainer to me.
There are things in my business that I understand very well, that my clients do not. I make a point of delaing with these things when thay arise.
You do make a good point about the effect of age on authority, its an example of something called "referent" power and it means power instilled by people choosing to invest it in someone.