That's because the reasoning that most men used is my "How will she react? Will she be angry? How will her reaction make ME feel?" paradigm, rather than the "What is The Right Thing to Do?" one.
This isn't Mother's Day, where you can rightly offer recognition of her role as the mother of your children, or even your anniversary, where you can do the ol' "If nothing else, we've had some great shared memories and these three beautiful kids" or whatever. This is VALENTINE'S DAY -- a day for lovers and romance.
And that's all PURSUIN' at this stage, for most of these people.