make more sense to build.
True its costly as hell but in the long term wouldnt it make more sense especially since it avoids pitfalls that subways have such as possible flooding issue like what happens from time to time in new york?

but they don't have that goal and don't have the money for it. They build streetcars as a way to convince developers to build shiny new buildings along the route. Lots of times, the construction for both happen at the same time. And when they finally accept that the streetcar is worse than buses and doesn't carry enough people (like a real rail system would), it's easy enough to remove the streetcar and drive on the roads again.

They've done this with bus rapid transit too, which is even easier to dismantle, but fewer developers are impressed with it. Streetcars seem to hit the sweet spot between cost and development incentive.