Why Wont Cities Build Subways Anymore?

Source: http: www.railforthevalley.com
I am in constant internal questioning about the reason why countries and more specifically cities stopped building subways if they’re “obviously” the superior method of mass transportation system. Why where subways more profitable in the past where technology and engineering wasn’t so advanced and now, they’re just too expensive? so I did a little research on the topic to solve this question.
After ending up in one of my go-to blogs http://www.treehugger.com/ I came up with an article called “Which is better for a city, subways or surface transport?” which talked about the differences of the subway system and the LTR or “streetcar” as it is commonly known. The article analyzes both systems for the implementation in Toronto and in it, a phrase caught my attention: “You don't build a city by taking people off the streets and sticking them underground, but by thinking of the bigger picture” the article goes on and on explaining why it’s better for cities to have people on street level, in contact with restaurants and shops, boosting the local economy up and creating dynamic and social environments.
What I understood is that subways are the most effective in long distance travel, but as I have discussed in this blog in the past, cities are following the trend of creating micro-neighborhoods, so the need for long distance travels within a same city is disappearing upon millennials. So, subways are still effective for what they’re made for, the thing is that what they’re made for is not so relevant now, at least not as much. Streetcars are the present of mass transportation as they take away the necessity of owning a car but won’t shove you in an isolated tube underground but will ignite integrated
communities and boost the economy.
Sources:
http://www.treehugger.com/urban-design/which-better-city-subways-or-surface-transport.html
http://www.railforthevalley.com/latest-news/zweisystem/subways-dreams-for-dreamers/