Why? Everyone knows that the American Name for something is better. For example we all know Flashlights are better then Torches, Elevators are better then lifts, Wrenches are much better the Spanners and Trucks are better the Lorries. Using the American name for something always makes something BETTER.
Just a joke on the differences between British and American English.
Other differences between American and British English:
http://en.wikipedia.org/wiki/Comparison_of_American_and_British_English
Map on American Dialects:
http://www.uta.fi/FAST/US1/REF/dial-map.html
More about American Dialects:
http://en.wikipedia.org/wiki/American_English
List of English Dialects:
http://en.wikipedia.org/wiki/List_of_dialects_of_the_English_language
Map of North American Dialects:
http://aschmann.net/AmEng/#LargeMap4Right
The above calls "Pittsburgh" a sub division of the Allegheny Dialect which surrounds the Pittsburgh Dialect. Both are close, with Pittsburgh having a few more sounds from overseas (and that is more an opinion by some writers then others, i.e. others call it both "Western Pennsylvanian" or "Upper Ohio Valley" but its extends the whole length of the Pittsburgh Seam of coal).
Here is a Dialect map of Pennsylvania:
http://www.evolpub.com/Americandialects/PennaDialMap.html
Here is a Pennsylvania Coal Map. The Pittsburgh seam is the bituminous coal field that goes south of Pittsburgh, but the Freeport seam was mined to the north. Thus a lot of workers shifted form one mine to an another, thus making a whole area one of the larger area in the Country with one dialect.
On the Coal map where the letter "F" is in field is about where Pittsburgh is. In the dialect map, Upper is underlined by the Northern border of Allegheny County. The County Seat of Allegheny County is the City of Pittsburgh which is in the center of Allegheny County.
Here is a Pennsylvania Coal map:
http://www.dcnr.state.pa.us/topogeo/econresource/coal/index.htm
I just was carried away by your use of the work "Tram" on DU, it is used a lot of DU and most DUer know it is the English word for the American word "Streetcar", but once I started to look up places to support the difference in wording, I was carried away by the topic.