I have to ask the obvious question... "Why is all men dying SUCH a disaster?" Well, short term anyway.
In the book, it’s all males, rather than all men. Beyond the severe shock this would cause regarding everyone’s son/father/brother/etc dying, there are countless practical implications. In the book, the point is made that most airline pilots are men, hence planes falling out of the sky. A number of nuclear programmes are male-oriented in terms of maintenance, which would cause power issues. Food supply would be hit extremely hard. And then there’s the future of a planet where the vast majority of species are on the very brink of extinction.
The book is a good yarn, but it was pretty light touch on all those things, I thought.