Having a baby

A man is on the phone to the doctor.

"Come quickly, doctor. My wife's about to have a baby."

"I'll come right away. Make sure you have towels and boiling water ready."

"Why, doctor?"

'Well,

Spoiler:

it's raining heavily and my car's broken down so I'll have to come on my bike, and I'd like a cup of tea when I arrive."