[zhoBEENG]

From an evolutionary fitness perspective, it makes sense as a kind of loophole for easily reproducing and distributing your genetic material in a way likely to lead to many successful family trees. This might actually be one of the best strategies.

[SvenL]

I think the issue is could be that your new partner might be your half sister/half brother which could yield some problems.

[zhoBEENG]

The lines that have these issues will be dwarfed by the hundreds that don't. It's scattershot for sure, but if it gets to the point where the rate of inbreeding is statistically significant to the total success of his genetic material, then he has likely already "won" the genetic game.