Over here in Europe we have Curve that does exactly that, without the fancy hardware: https://www.imaginecurve.com

Anyway Plastc was about trying to actually emulate a card. All this has been leapfrogged by Apple and Samsung Pay.

Europe has capped interchange fees to 0.2% and 0.3% for debit and credit cards respectively. However, three-party schemes (like Amex) and corporate cards are exempt and charge more. But you're right, I'm not sure how MasterCard is happy with that (since the product is clearly targeted at consumers).

If they'd had a whole lot of market share already, maybe they could have persuaded issuers to provide private keys in some way that could be imported into the Plastc device (which might itself then have a tamper-resistant smartcard processor like the one in the individual chip cards).

Even three years ago, the writing was surely on the wall that they were exploiting weaknesses in old tech to pull off their product, so there was an obvious sunset on their ability to operate their core product. Why would they invest in something that already has an end date on it?

With tap + debit, I can track all my individual transactions via services like Mint, plus my bank sends me an email on every transaction that happens to my accounts, so I have redundant logging of where all my money goes.

I don't know the tech behind it but this Dutch startup is doing exactly that: https://www.bunq.com/en/

"To rip it off, someone would have to get into the physical chip circuit and manipulate things to get your bank information. Not only is this level of data surgery really difficult, but it also requires a set of high-tech equipment that can cost north of $1 million."

https://tinkerings.org/2015/11/15/in-which-i-acquire-a-scann...

And as for "far beyond average hardware hacking skill", I suspect if you got Bunny Huang, Michael Ossmann, and Travis Goodspeed together and curious - this might well be broken in a single weekend! ;-)

I have no idea why they went under.