"Trapping a man" is an antiquated notion stemming from the days when unwed mothers and their offspring were ostracized by their friends, some family, the church, and were isolated and alone. The "honorable" thing to do if a man impregnated a woman was to "make an honest woman out of her" by marrying her.
It used to work very well, but now there is little stigma in being a single mother and even less in being an uninvolved father.
Women do actually use that tactic and I, like Ebony Rose, am acquainted with some who have. IMHO, the difference between then and now is that back then, two people really loved each other and birth control was not very reliable. Many children can view their parents marriage license, do the math, and realize that the marriage was subsequent to the conception. That was not entrapment.
With all of the ways to avoid pregnancy and the difficulty in finding a suitable mate in the first place, some misguided and desparate women believe that getting pregnant can lead to marriage. The irony is that some women believe this even if the man in question already has children without benefit of marriage.
Just another glaring example of how the family unit is deteriorating.