I believe when the early Hollywood producers visited the saloons
in what was left of the "Old West", they encountered coin pianos
(which were new to the scene -- as these producers must have assumed
they were always there) and so they were included in the interior
shots of early silent films.

Later on the coin pianos were used in saloons in places like Knott's
Berry Farm and the Last Frontier in Las Vegas, so the ubiquitous
saloon nickelodeon became a part of the Hollywood lore and myth of
the "Western."

Stephen K Goodman - Professional Player Piano & Nickelodeon Restoration
Tarpey Village (Fresno/Clovis) California, USA
http://www.mechanicalmusicrestoration.com/ 

 [ What are the titles of some early "Western" movies that show
 [ a barrel piano or a player piano or coin-operated piano?  What
 [ is the accompanying sound?  ;-)  -- Editor (Robbie)