http://www.slate.com/blogs/future_tense/2015/07/30/convertin...
http://www.theatlantic.com/technology/archive/2015/11/why-do...
It mostly seems to boil down to budgeting woes and bureaucracy. And in having one of the oldest subway systems in the country with a ton of technical debt to deal with.
Expensive expensive expensive.
They would have to replace all of the turnstiles (for some reason I doubt they could retrofit them) which is a ton of turnstiles. The MTA subway is BIG (as far as I know, bigger than SF and Boston, in terms of number of stations).
They would need dedicated central servers to handle everything, unlike they have now, which the article says "complements" the existing system but which is not required for operation.
MetroCard came out over a decade before CharlieCard (Boston) so they have tons of infrastructure that would cost an absurd amount of money to replace. I imagine they figure it isn't worth it, especially when there are so many other subway projects that need money.
A central server can be used for things like web-based reloads and auditing, complementing the system... but it's entirely possible for a terminal to remain in offline-mode and just check-in at the end of the day to get any pending messages and upload logs. This is why it takes longer to reload/unblock a SF Clipper card using a reader in a bus (offline mode) as opposed to at a BART turnstile (online mode).
It doesn't even need to be held in anything secure, you just need to sign the balance when writing and check the signature when it's used.
So a bus turnstile can do transactions when it returns to the garage, and turnstiles in locations where it's hard to run data for whatever reason can get a plug-in every so often on a regular maintenance run.
It'd be far from easy. The cost and magnitude of a project like this would be enormous for the entire subway system, and the MTA is not without bureaucracy. As others have pointed out, the subway has far more pressing modernization issues that rank higher than this.
I lived in London for several years before moving to NY this year and the failure rate of swiping my MetroCard is about the same as touch issues with my Oyster card / contactless debit card in London. While it would be a great advancement technologically, there really isn't a pressing need to replace the swipe card anytime soon.
There are definitely many advantages to contactless cards, but I'd rather the MTA focus their efforts on something with much more of a benefit. E.g., real-time train information, something that also requires a huge infrastructure change, but one that would have a greater benefit to travelers.
http://www.theverge.com/2016/4/12/11416362/mta-nyc-fare-paym...
So, considering how gov software projects tend to go, it'll probably cost $1.5 billion and come out in the early 2020s.
http://www.nydailynews.com/news/world/london-contactless-oys...
2) The MTA is a perpetually underfunded, poorly governed monstrosity whose construction projects cost many times more than any other comparable metro system.
3) The MetroCard still works, as clunky as it occasionally is.
The MTA spent a lot of money in the very early 90s getting the system installed only for Ethernet to take over pretty much immediately.
Considering how old that software stack is, it's remarkable how well the MVMs run. In 19 years of buying MetroCards and riding the subway, I don't think I've ever had one break down on me. I've had my fair share of scanning errors and bad cards, but I'm more inclined to blame that on the quality of the magnetic strip and normal wear.
Here's a recent bluescreen - only the second I've ever observed.