I remember reading somewhere that the shape of the (human) penis head is designed, or, I guess has evolved to, when pumped back and forth in an encompassing channel (you know what I'm talking about here) it works to remove semen already present. I look at the shape of the head, the slope of the egde, and imagine what would happen in that 'channel' and (I usually get hard, but that's not my point) I can see it.
So, it may be that we've evolved with this as part of our nature.
I'd do it.