Whilst not in full agreement with L337's description of events that led to the accident to N90AG at EGBB last January, the AAIB final report will no doubt answer the key question posed at the start of this thread.
Please do read it carefully.
The first knowledge I have of accidents caused through a lack of de-icing goes back to the 1930's when a flight of military aircraft took-off from a field in Scotland. All came back to earth with a bump! It was a relatively new experience in those days to discover the effect of ice and frost on even basic aerofoils, let alone super critical wings.
Why is it we are even still asking the question - do we never learn!