Here's a nice piece from Adam Nagourney about efforts to upzone Hollywood in Los Angeles. This is a long story that can be made relatively short. Basically, the city of Los Angeles now has a decent-sized Metro system. You sometimes hear from Angelinos that the Metro "doesn't go anywhere" but that's not really correct. Rather the issue is that Los Angeles is very large. With a metropolitan area triple the size of Boston's, a Boston-sized rail system serves a relatively small fraction of the city. But it still serves a lot of people and places in absolute terms.
The main reason that cities invest in rail infrastructure is that transit can support a much higher throughput of people than can private cars, and rail can drive real estate investment in a way that bus routes can't. So the reasonable thing to do is once you've built your Metro stations you need to upzone for higher density and less parking so that dense construction can take near the stations. If you do that, your investment in transit will pay off and pave the way for further investment and further growth. If you don't do that, you've basically wasted your money since LA Metro continues to run at a relatively low capacity. Hollywood is now home to a number of stations along the Red Line, creating the possibility of transit commuting to downtown and, over time, the construction of a dense walkable neighborhood. This is especially true because in Los Angeles' pleasant climate, walking around is actually a much more doable proposition than in Boston or Chicago.