Back in the day refiners got a lot less out of the crude, these days the recovery rate is far higher leading to a "drier" less lubricious fuel......not very good for injection systems.
Sulphur reduction for the environment took out something that was a lubricity enhancer and a natural biocide .....not good for injection systems or for storage.
Tightening emission standards pushed up injection pressures with finer tolerances and lighter needles...... which probably would have loved the old high Sulphur gas oil.
When the need for better fuel crossed paths with a declining suitability some bright spark thought that adding a bio element would be a good idea.
So we now have a fuel that naturally degrades with a whole lot of fats and waste plant oils added that provides a perfect dinner for microbes.......it's actually amazing how well modern engines do survive
Fuel additives above the very basic level supplied are increasingly looking essential