You get a good credit score and still live within your means while also getting additional points + bank covering any fraudulent activity if the card got stolen.
Of course this method probably won't work for people that feel they would rather just cut themselves off from temptation fully or those without access to banking systems, which I sympathise with.
I did this for a while after being bitten a couple times for not having a credit history.
However, I recently stopped. I still keep one card around and active just to maintain my score… just in case. However, spending $10k for $200 in rewards… I don’t really care. That’s mostly a tool to get people to justify more spending.
I’ve quite liked using the debit card and seeing the number go down when I spend, it makes more sense intuitively, and I always know exactly what I have. I had a debit card stolen about 20 years ago; I was able to get the charges reversed, no different from a credit card in my experience. It’s on the Visa network.
I would cancel my last credit card, but I don’t want to deal with cell phone deposits and other nonsense, like I had to in the past.
Anyways, from the little research I've done, it's certainly illegal and not a proper mechanism for authentication. One can dream though :)