What Rutherford instituted in his tenure works for the Borg.
Celebrating any holiday takes away focus from the Borg.
It works to this day.
Same applies for birthdays,,mothers & fathers days.
Just think of the focus the Borg would lose by shifting focus away from ""them" to allll those birthdays. Also mothers & fathers days. Not to mention statutory holidays.
It works for the Borg. Why would they want to change it now? It takes focus away from them.
And,,,$$$$$,, money too.