Thank you, Magnum, for raising this question. I have observed the same thing here, but hadn't formulated the sense of it into words such as you have done.
As an inactive, occasional Sunday meeting attender, I regularly discuss something relative to the public talk or WT study with friend or stranger (speaker or JW of new acquaintance).
The thought never occurred to me that a Witness would be hesitant to discuss the Bible. Well, younger adults raised in the Truth seem disinclined. Yet I note, likewise, that amongst the friends in general -- even older ones -- there is nonstop talk about so-called worldly things: entertainment, trips, recreation, etc. We have lots of pioneers, and I am aware of their "spiritual" works AND extra-curricular activities mainly through Facebook.
Maybe the fire in my bones doesn't permit them an opportunity to broach Bible subjects of their own accord. To be fair, there are several I know personally whose lives truly focus on theocratic pursuits and discussions thereon.
CoCo