Long before even the CONCEPTION of the cel phone (in April 6, 1929 to be exact), the Telephone Message Bureau produced a lot of advertisements about men answering phones in public places. Curiously they always depict the "candlestick" style as opposed to the Bell 102 (or "French phone"), maybe to make the image more striking.
This advertisement states "you can't phone on the subway. It's too noisy." But either subways have gotten quieter or it's no longer "too noisy" to answer your phone there, because everybody's doing it.
Note the expressions on the faces of the passengers: the man on the left is rightfully annoyed to be listening to the details of Mr. Telephone's house party ("Dude, she was totally DRUNK, like totally GONE, like twenty-three SKIDOO!"), but the guy on the right thinks it's all very funny, and the woman at the far end is just afraid her fox-fur stole is coming back to life.