Sure, but in the spirit of longevity, you're talking about a stop-gap solution at the most. There's also this: they aren't solving a real problem. My wallet going from 1 inch to 1/2 inch isn't a selling point.
I'll give you your second point. I bought one because I thought it was neat. If I can reduce the size of my wallet, then sure, that's great, but the biggest draw for me is "OOh. That's neat tech, how did they fit it in a credit card?"