"Security" in this context means a woman taking comfort in the knowledge that she will get 50% of your assets in case of a divorce. This isn't much different from a lender securing his loan with a mortgage.
If you look at marriage as a commercial transaction, where a man buys a woman and the consideration given for the purchase is half of his future assets (or whatever is negotiated under a prenup), it kind of makes sense. The main problem is the modern concept of a "no fault divorce". A woman can decide to terminate the marriage contract at any time (and statistically speaking, 80% of divorces are initiated by women) and still get her pay out. This has no analogy in the commercial world. When a bank gives you a loan, it's for a fixed term. As long as you make monthly payments, the bank cannot recall the loan. Now imagine if a bank gave you a loan for a 10-year term and then decided to cancel it after two years...and you would be liable to not only pay back the principal amount early but also interest on the full 10-year term, even though you only had the money for two years. This is basically how modern divorces work. The end result is that while marriage might give a woman a sense of security, it does the exact opposite for a man. A married man is, by definition, financially vulnerable.
Of course, the above analysis only applies to men with some financial means. If you're unemployed or a paycheck-to-paycheck type without a dime to your name, you don't have to worry about any this. Perversely, the only way a man can feel secure in a marriage is if he's got nothing to lose. Of course, the woman's "security" isn't worth much in that case. So at the end off the day, it's zero some game. Either the woman is secure or the man. But it can't be both of them.