I think a (the?) major one is that of providing riders with real-time information about closings, reroutings, etc., that was previously pretty hard to get without physically being present in a station.
And then there's me, watching the trains enter and exit the stations in real time. :-)
I got to love the city many decades ago, as a young software consultant. Oh, the smell of urine and the sight of graffiti on the trains and garbage in the streets! I still love it, but you're right, it is quite a different place. In some ways better; in others, worse.
At least singapore keeps it clean, despite my hatred for non-private transport. NYC does a great job of cramming humans into close proximity with literal bubonic plague rats