Some referees in my local league used to enforce the tuck. You knew you weren't getting away with any shenanigans in those matches.
To answer the OP, I'll put a date of November 23rd 2004 as the date that untucks first exceeded 50%
You might of actually cottoned onto something here?
Aesthetically was it the skinnier footballer not tucking in? While the rest that loved a Tuesday club would tuck in?
As football has got so sports sciencey and they all drink there own pee...