The spouse gets 1/2 the increase in value during the divorce as a barganing point.
A qualified divorce resolution order (QDRO) generally sets the disolution of marriage value.
I think most of the nest egg planning is to have cash on hand for the divorce proceedings. This allows the man, who usually is booted out of the house to be able to find a place to stay, and retain a lawyer.
I sympathize with those who say this is preparing for the worst without working for the best, but I think it is not unwarrented to take these steps.
Why should any man wait to marry to buy a house, start retirement plans, or have cash on hand. If it was women we were talking about, there would be no "debate".
Over the years, I have known some married women who referred to their "get away money", or "escape money". The implication was that money was squirreled away "just in case". I remember some of the revenue streams were quite ingenuus :)