Q4W: What reasons are there for why you believe a man would desire to raise another mans child

Question open for men who raise/have raised another mans child also:

If a woman already has a child, then the mans resources could be spent on raising his own child. Even if the woman is open to having a child with that new man, it will mean that his resources get split between his child and someone elses.

If a man cant have a child, well why waste resources on another mans child. But a cabin instead and hunt bears and climb mountains. Your going to wiped out of the genetic pool anyway so why not enjoy the end of you lineage instead of doing another mans job.

Neither man or woman can have child, see above, why spend resources on another couples child as opposed to enjoying the end of your lineage(s) together.

Scenario where this may be different.

Death of relative who has child. This child is still your blood, so if your all thats left, then there is some duty to carry on your lineage.

I fail to see any value or improvement of life derived from raising another mans child.