The RFID cards, however, are far more durable than the flimsy MetroCards that NYC uses.
I keep all the cards from cities I visit though, since more often than not I end up passing through the city again within a few years. Some cities' cards unfortunately expire and eat all your balance, while others keep them for 10+ years.
It's really nice though to just land at an airport and be on your way in minutes without fumbling and getting in line.
On another hand I kind of miss the subway tokens that Boston used to use a long time ago. One of the advantages of tokens is that they are very much like NFTs in that if you have a token, it is a promise of a ride, any time, now or in the future. So you could also use them as an investment vehicle by buying 1000 of them, and the transit agency gets 1000 * (fare price) in liquid cash upfront that they can use to scale their infrastructure and make upgrades, while you can re-sell those tokens at a profit 4 years later. Or if you were arriving in Boston for college, you could buy enough transit ride tokens for 4 years upfront, if you were smart. Unfortunately with the RFID systems they don't usually pay dividends or interest on the balance on the card.