Do you have any specifics?

Every marriage is a different case. You can't pass a general statement. And even they are different in different cultures. Women have different types of responsibilities to perform than men in a marriage. It's not fair and easy to undermine one sort of work/duties.

The important thing in a marriage is love. Marriage is not a business contract, where you should measure profitability. Some things cannot be measured/compared.

From what I've seen men get most of the benefits from marriage.

Let's examine the reality:
The "50/50" relationship, or equal partnership, always and ONLY includes help with cooking, cleaning, laundry and grocery shopping. The 50/50 relationship, or equal partnership, NEVER includes help with vehicle repair & maintenance, heavy lifting, yard work, home repairs, appliance & maintenance, or plumbing & heating repairs. "That's a man's job!"
Seems to me that women benefit at least 50% more than men.

Um research actually shows that marriage is a risk factor for women and a protective factor for men. Marriage provides men with the emotional and social support they need so they're less likely to engage in risk taking behaviors. Whereas child birth and household chores can be tough for women. They may be looking at the financial aspect which does benefit women more.

The only thing I got out of being married was my amazing son and I definitely seem to recognize that much more than his dad.

Because they want to eat their cake and have it too.

hmmm

Because that's its purpose, to protect kids and gals from the powerful and violent men.

People who say this are usually focusing on the benefits they believe women receive and overlooking the many ways men benefit. In a healthy marriage, both partners should gain from companionship, support, and shared responsibilities.

Maybe because they're misogynists and base their ideology on Victorian morals and ethics??