I agree with you, they are very cool. When in a town that has access to an actually trolley line I always find an excuse. A few are very useful (San Francisco, New Orleans), but you're also right that most are just vanity projects. The stops being too close together make them slow. The length makes them impractical. But - they still can draw people. Kansas City put in a great route going by a ton of awesome attractions and connecting districts that otherwise never really worked together (think Cherry Street and the Blue Dome, not really that far apart... but totally separated). The cars, live route information, integration with Google, and price point are all awesome. Ridership is strong at 6800 a day and development along the line is booming ($1.5 Billion proposed or constructed, with about half of that saying the street car was a major factor). KC did it right.
Voters declined to expand the line in 2014 by a 60-40 margin. Private industry funded a study to expand the line down Main past the City Center, WWI Museum, through Westport and on to the Plaza. Making their starter line into a respectable transportation line! Elections are set for 2017.
http://kcstreetcar.org/about-streetcar/streetcar-expansion/But to illustrate the issue using your KC example, the trolley ride from the President Hotel to the Market takes 10-20 minutes, depending on if you catch the trolley or have to wait on it. If you were to just walk the 12 blocks it would take ~18 minutes. Your hotel is at the mid-point of the route, so going to the WWI Museum on foot takes ~30 minutes or 20-30 by trolley (you still have to walk through Union Station and up to the museum).
https://www.google.com/maps/dir/''/City+Market,+KCMO,+MO/@39.103016,-94.5863923,16z/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x0:0x285f54100d1868fe!2m2!1d-94.5841292!2d39.0975267!1m5!1m1!1s0x87c0f08ae74d9b29:0xabf79f6e3b419841!2m2!1d-94.5818625!2d39.1084649!3e3
Arguably its a break even on time... but the cost of $102,000,000 plus up to $4,000,000 a year to operate it really adds up (bond maintenance is $4.4 million, funded with a sales tax in within a certain distance of the line). So the total subsidy is $4 per rider, so you and your wife riding the trolley to the market instead of walking cost taxpayers $16.
http://www.kshb.com/news/local-news/investigations/a-streetcar-desired-doing-the-math-on-how-the-taxpayer-funded-kansas-city-project-adds-upYou did add economic activity, but probably not $16 of profit to the overall economy. Some conferences might decide on KC in part because of the line. Some projects, business and some residents might locate near the line. But it is hard to calculate if it is a solid investment just relying on return of investment. Now, you can add to that the ability to increase density in an area, the savings in infrastructure on expanding roads or sprawling the city out, and the increased revenue possible from a given section. Also, you have to add in quality of life benefits. Would the expanded line allow some to become single car families, help kids get to piano lessons, school, or a job? Finally, the overall synergy that can come from a well done municipal project - it seems doubtful that the Convention Center actually pays for itself, or the large arena, or the freeways for that matter. But they are a vital part of an integrated system that helps drive the economy.
I think if they expand the line as they hope to, it will pay off handsomely. As it stands, the short line is a vanity/tourist project - one that is more useful than many... but not much more than that.
But all that said, I still want to see it in Tulsa.