Why are children of married parents valued more than those of single parents?

When a married couple has a baby everyone is usually just happy and there are no complaints. The child is wanted and loved by everyone and they are all excited and happy for the parents. Those children definitely come into the world knowing they are loved and their birth is a celebration. So they have a good chance of growing up to be well adjusted.

Now when a child is born to a single mother, everyone is angry or disappointed. They always claim they care for the child and don't want him/her born into a difficult situation, but maybe this is why single parent families struggle more. Maybe the baby in the womb can sense that he/she isn't as valued as they should be. Even if a married couple is very poor, no one says anything about it because you can't expect married people not to have s*x. But with single mothers it's always wrong if you're poor. Everyone is always eager to help out with 2-parent children because it's a cute little baby. But a single mother's child they say "she did it to herself", even if she's asking for the same emotional support and assistance you just gave to the other parents.

I just wonder if the attitudes of other people can influence the child's future. Some are thought of as a blessing and others are thought of as a problem. That's the way it looks even if no one wants to admit it...it is harder for single mothers but I don't see why that's a reason to devalue a child. It's like 2 parent children have mother+father+immediate family+long distance family, while single parent children sometimes just have mother.

They think they are looking out for the child but really by talking to the mother the way they do, the one who is raising him/her, they are affecting the child's self esteem.

NOTE: I know that not every single family works the way I have said above, this is just the average thing I have noticed.