It is a flexible, non-prescriptive tool which has been shown to save time, money and workload by an EU working party.
[1] Diploma Supplements were gradually implemented at European universities as part of the Bologna Process, since approximately 1999.
However, even as late as 2013 there were still some European universities, who despite their country's years-old membership of the Bologna Process, had not yet finished the necessary procedures for issuing Diploma Supplements to their graduates.
It is important for countries and educational institutions located outside of the European Higher Education Area to realize that Diploma Supplements cannot be retroactively issued, hence why students who graduated before their institution's country became signatory to the Bologna Convention cannot possibly have a diploma supplement for that degree.
Consequently, requesting a Diploma Supplement from a student who graduated from a European university in 1995 or earlier is not possible since the Bologna Process was not even in place before that date.