I don't know when I first heard students boasting about these scare away intro lectures [0] but it was noticeable by the early eighties.
I've a few unsubstantiated hypotheses why:
Zero Sum Game taught by boomer parents conscious that the party was already over but would be sustained inevitably with increasing ruthlessness.[1]
Intellectual Property laws started slicing and dicing knowledge that became temporarily more valuable by fencing it in.
Higher Education caught performance metrics (without much if any performance pay) and so especially elite schools but eventually the rest cottoned onto input pre selection as a way of surviving.
Society became a overt lottery particularly for low income families. This placed the easy weight of the burden of responsibility of tutors on the side of direction to easier subjects.
I believe all these factors and more began compounding exponentially with the enclosures act imposition of a requirement for a degree for work with no or marginal utility for the same.
Marketing, loans and for a particularly insidious enclosures act, the UK's "classless society" introduction of University status not only for a tsunami of new institutions (the UK will now accredit degree granting university status in only two years..) and the white washing of the vocational STEM/ Engineering focused UK Polytechnic system (making them independent degree awarding institutions enabled diversification and dilution) which multiplied the demand for least effort maximum passing grade tertiary education throughout the world ,by the turn of this century to lamentable result.
[0] turning up next week seems to have been the objective of one I spoke with, to demean the honest and intimidated.
[1] The last market play I laid on with my late cofounder was in reaction to the dotbomb. Bought military tech suppliers :-| Point being we need the new program before we are fully grown up so to pass it on. With massive shifts to younger population and the current generation of middle aged folk being capitalized by three bull cycles the last two payable like a Japanese 80's mortgage, by the grandchildren, this means now.
Edit: second footnote placed and "enclosures act" gains a act adjectivally. Edit2 for work para7 Edit3 last para payable not relatable.