Why would someone rob a sperm bank?

A masked man goes into a sperm bank, points a gun at the woman behind the counter, and says, "Open the safe."
She says, "This isn't a real bank, it's a sperm bank."
He says, "Open the safe or I'll shoot."
She opens the safe, and he says, "Now take one of the bottles and drink it."
After she opens the bottle and drinks it, he takes off his mask and the woman realizes the robber is her husband.
He says, "Now you see? It's not so difficult, is it?"