It was one of the tools that allowed me to maintain healthy credit card usage habits. In my idle time when messing around on my phone I’d gotten into the habit of just transferring money from my checking account to my credit card, often in excess of my actual balance, so as to cover “pending” purchases.
Not only will my bank no longer let me do that, just to twist the knife a bit, they will let me make multiple payments totaling the pending total due so long as no individual payment exceeds my actual balance.
So it’s not that they can no longer handle negative balances on the card, it’s just that they’ve half-ass made the interface disallow it.
I did this with one of my cards just the other month because of this exact reason - it was due in the middle of the month instead of at the end/beginning like the rest of my accounts, and it slipped past my radar once. Now it’s due on the 28th with half my bills.