Also about penises.....
The shape.
Scientists have been studying the functionality of the shape, and no surprise, just like almost all other mammals, our penis is shaped so that it can push out a rivals load to replace it with our own. Its akin to the theory as to why a cat can have multiple breeds in one litter, except with humans its the fastest swimmer wins.
So big or small, it has more purpose than just simple injection of the sperm.
Also, looking at the shape of the penis and then the interior of the vagina, up to the cervix, its built to fit, and was theorized at one point to lock in, to work almost as if we had knots to inflate, as evidenced by the further expansion during climax. The slight growth triggers the vaginal walls to grip harder and lock it in place, hence part of the "blackout" of thought effect mid to post coitus.
In other words
Men are meant to fuck, lock in and do the job to the end.
Funny.