Clyde Dunbar’s wife drew for him because he couldn’t attend.

Clyde Dunbar broke his leg and is not able to attend the village’s annual lottery.  This does not get him out of it, though.  There is a rule about who draws when a person can’t.

"Me. I guess," a woman said, and Mr. Summers turned to look at her. "Wife draws for her husband." Mr. Summers said. "Don't you have a grown boy to do it for you, Janey?" Although Mr. Summers and everyone else in the village knew the answer perfectly well, it was the business of the official of the lottery to ask such questions formally.

Mrs. Dunbar tells him that her son is “not but sixteen yet” and therefore cannot draw.  She will draw for her husband.  Asking about her son is just a technicality.  Everyone knows everyone in this small village.  They are fully aware of the fact that the Dunbars do not have an older boy.

Apparently, there are other boys who do draw for their family members.  The society seems to be patriarchal, giving precedence to men and older boys.  This is why the “Watson boy” steps forward to draw for his family.

A tall boy in the crowd raised his hand. "Here," he said. "I'm drawing for my mother and me." He blinked his eyes nervously and ducked his head as several voices in the crowd said things like "Good fellow, lack." and "Glad to see your mother's got a man to do it."

It is an interesting dynamic.  No one can escape the lottery.  Illness and old age do not matter, or any other kind of incapacitation.  There is a preference for men.  Maybe the patriarchal, man-centered society is a result of the village’s reliance on tradition.  They do not like change at all, or they would discontinue the barbaric lottery.