"Because it benefits so few people--only 3% of people take transit to work".
And how many people took automobiles to work in 1917*?
That's right. Because we have no idea.
We know that about 30% owned cars. (No idea how many had access to transit--have to find that out someday)
Compare that to the number of people who were riding transit at that time:
In 1917, there were 14 Billion transit riders, so about 131 transit trips for every person in the United States. Sadly, no data for auto users, so we still can't make an apples-to-apples comparison.
We have some estimate of how many automobile miles were driven: About 30 billion. Or, for a U.S. population of 106.5 million, about 289 miles a year. With 260 working days in a year, that is about a mile a day.
Data for transit is proving difficult to find, and even APTA doesn't have it for before the 1970's. The best they've got is vehicle miles**: In 1920, there were 1,922 million vehicle miles (1,922,000,000)..but that's just how far the trolleys traveled, not how far the people on board them traveled. Without knowing how many people were on board, we can't compare person-mileage.
*Streetcars reached their apex in 1917, the same year Federal funding of roads started. Whether the Feds just switched to what would have been the winning horse anyway is difficult to know.