I think I've solved the mystery- I've unearthed the reason for our students' "lack"of comunicative capacity in English. The reason- most of them are not used to really expressing themselves in Portuguese to begin with.
How many times when I ask people to give an opinion about anything, anything at all, they start off with
"Ah, psh.." with a typical shrug of shoulders that indicate their total indisposition to go into more detail, or to really say why they agree or disagree with an idea.
So, they come into the EFL classroom and we humble teachers unknowingly ask them to really say something.
How do they react to our "stimulus"? "Ah teacher, because..." "Teacher, you know..." and the rest of the sentence or the idea is left in oblivion.
Some even award us with the movement of the hand- forefinger and thumb open, they move their hands as if they were holding a doorknob. Their gestures are supposed to after all, say what they mean non-verbally. The catch is that hardly ever works efficiently.