To protect forgetful fathers.
I've shared Mother's Day thoughts previously; here's a new reason. For the father(s) who may have awoken Sunday morning, having inadvertently forgotten the national day, it's not until they get to church that the error of their ways is exposed. And when compared to the curve-wrecker fathers whose mothers/wives are gushing about the pampering they've received, it can turn into an arduous morning.
Speaking of which, how come we accept Christmas shopping for loved ones all the way up until the last minute on December 24, but family members who are out at the last minute on the Saturday night before Mother's Day are looked up with disdain?
For the record, we celebrated Mother's Day with my Mom and Oma on Saturday evening. :)