For every complex question there is an answer which is clear, simple and wrong.
An explanation for why men and women are now the same, (men and women having been a sort of simplification for bigger and smaller people).
The new guidelines recognise that while long-term alcohol-health risks are generally higher for women than men, men face much higher risks of acute harm (e.g. injury) on single drinking occasions. Therefore, it has been decided to set the lower-risk level at the same amount for both.
They have combined our risk of injury due to being drunk with the increased risk of cancer.
So my pint of beer watching TV at night puts me at risk of getting into a street brawl!
The 14 units was picked as the point at which a the risk curve passed the (arbitrary) 1% risk figure, if they had chosen an (arbitrary) .8% risk or an (arbitrary) 1.2% figure then the recommendation would be different.
So plenty of scope to "fiddle" your own maximum limit by choosing an incrementally higher or lower risk level, by making some compensation for your weight compared to the average and your ability to avoid fights, accidents etc after drinking.
While some may disparage a 1% risk, that does mean
half a million people* potentially saved from cancer by following this advice.
*if you assume
everybody would drink to excess without it.