"Why oh why do women allow their dh's to go off on these absurd stag do's"
Because you don't control or own your partner.
It should be agreed in advance, once you have children that you are both still allowed free time, including trips away.
All of my friends (female) go on these type holidays, life doesn't have to stop because we become parents, or have partners.
I know men who do, do recreational drugs and have used prostitutes in their younger years, but most stag do's are about the drinking, unless they regularly use drugs, anyway, they don't bother.
A personal spending budget, should be set, but allowances should be made to attend the events of friends and family.
I, as a woman, would find it impossible to live with many of the attitudes towards spending/nights out/having a life outside of the home/enjoying myself and the company of others/gift giving etc that many on MN have.
You have to keep a roof over your head, but life is for enjoying.