Funny. I just listened to a lecture about streetcars in my city. The owner of the first streetcar company just happened to be an at-large councilman whose family happened to own the farms adjacent to the route the car line took.
Streetcars, in the sense that they're being implemented in North America are no faster than buses in mixed traffic. What they mostly lend is the idea of permanently high frequency transit, which is a positive sign for developers although not as useful for residents as light rail.
These lines stuck around until the late 1950s, and had dedicated lane ownership. The city I live in is small and was demolished by urban renewal, so as suburbs that were a 15 minute drive away developed, the system declined with the central business district.