btw, it seems that no one has mentioned that the metro card system is a mag stripe based card and is over 20 years old. The equipment is starting to reach end of life. For example, the vending machines for metrocard run on Windows NT.
The biggest benefit to all this is never having to use one of those slow-ass, badly-designed machines again. They're not only slow, the UI flow is absolute trash. I find it a lot easier to just hand my local token booth guy a couple twenties and have him put it on my Metrocard. He even did it extra quick the other day when he saw a train was rolling in 🙏