That bothers me, because what this couple needs is for the husband to get some actual therapeutic help with getting his own sperm "up to speed" so to speak, rather than having his own father take his place.
That's one of the (many) ethical problems with all the artificial reproductive techniques: once you rely on them, nobody's motivated to try to solve the original problem, which is to aid this husband in regaining his natural fertility.
KRAMER
Jerry. Did ya ever have your sperm count checked?
JERRY
No, why should I? I wear boxers.
KRAMER
You ever get a woman pregnant?
JERRY
I'm sorry, Kramer. Those records are permanently sealed..
KRAMER
What would you say if I told you, "I never impregnated a woman"?
JERRY
Really? You never slipped one past the goalie in all these years??..
Boy, I'm surprised. You've slept with a lot of women, I--
KRAMER
A lot of 'em! [wild gesture, freaked out]
Do you think maybe I'm.. Depleted??!!
JERRY
Well, I'm sure you're not.. Totally Depleted.
KRAMER
Well, but what if I am? I'm the last male Kramer! We're facing extinction!
JERRY
Well, go to a fertility clinic. Have your sperm count checked.
KRAMER
Yeah, but then I'd have to.. well, you know.. into a cup? In the of the day??
ELAINE
Does that conflict with your regular schedule?