Why do single moms expect the men they are dating to pay for their children?

OK, when I was dating I encountered this a lot. Dating a single mom, she eventually expects you to pay for her children too. It's why I changed my dating requirements, I started to refuse to date single mothers.

Before some professional victim (leftist/feminist) chooses to attack me here. This is only and specifically about dating. Once marriage happens, if i chose to marry a single mom (thank God I didn't) I would absolutely treat her kids as if they were my own, I have no problem with that. Children are innocents and deserve love regardless of genetics. I would never tell them that I am their father, as I cannot replace him, and would not want to, but I would do my best to be a good father figure.
Why do single moms expect the men they are dating to pay for their children?
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