Soliek,
Why would it have been okay to eat tarfus in the 1950’s?
My understanding is that
a) food production was simpler then
b) it took a while after things became more problematic for people to realize there was an issue.
There’s no question that someone who eats processed foods (with few exceptions, packaged chocalate bars not being one of them) is being mezalzel in issurim (or in a small minority of cases, grossly misinformed, see hello99’s post), and that “something is up”.
BTW, I think you used the word “dearth” incorrectly.