In "Hills Like White Elephants," why do the characters and the narrator refrain from speaking about the operation explicitly?

The
characters refrain explicit discussion of the operation, aside from the man's brief discussion
of it, mainly because it is an ongoing discussion, one the details of which they are both well
versed.

"Its really an awfully simple operation,
Jig," the man said. "Its not really an operation at all."

The
girl looked at the ground the table legs rested on.

"I know you wouldnt
mind it, Jig. Its really not anything. Its just to let the air in.

The girl
did not say anything.

"Ill go with you and Ill stay with you all the
time. They just let the air in and then its all perfectly natural."

It is not the first time the discussion has been...