Why the ommission?
.. probably lost out to the popes new saints
They would receive no additional benefit from a front-page Mothers' Day article, since they already have nailed down all the advertising revenue they are going to get for this observance.
Besides, there is a mother-centric article in the Life section, page F1 and a whole page in color of various tributes to mothers who have passed on (page F8).
This should be enough mother stuff for you or anyone. If it is not, then start your own paper and mother it up to your heart's content!