People who deserve it the least of all seem to be cheated on with a special cynicism. The reason is quite simple: these partners are taken revenge on for choosing them, for being satisfied with an average level, for not daring for more. It is a self-revenge.
Women’s infidelity harbours a very unpleasant effect for men: adultery makes her independent without being lonely. Very harsh words unfaithful women are called express the fear the male part of society experiences in front of women’s freedom.