"Our direction when what we wanted to was make sure players have a way to really be in the world and have an immersive way to travel through the world," said Sasko. "This is designed to be a role-playing feature."
I used the modded Metro System for my playthrough along with a mod that adds basic primary needs (hunger/thirst/sleep). Many of my favourite moments were realising it was late after doing a gig, hopping on the metro and watching the city as I rode back to the apartment for a night's sleep.
Small things like that really help me with immersion, so I'm really happy they added this officially.
I forgot, you also probably want to get a modded timescale. I made my own custom one, but if you use vanilla you risk getting on the train at midnight and coming back home at sunrise. Here are some to choose from if you don't want to set up your own.
It was modded in by fans well before now, so it's definitely a wanted feature. People like immersing themselves in the city ambiance, and with good reason. I personally rarely fast travel, or even drive, because there's usually a lot more to see by just walking around. Convenience isn't a big priority in a game like this.
Its the same idea for stables in skyrim. Using them isnt ideal for speed, but there are users who prefer getting around via natural means rather than fast travel.