The customer/client/student has a problem, and they’ve brought that problem to us. We didn’t cause the problem, and it’s not our job to fix it, either. We get to say, if we want to, “it’s not my fault.”
But the person who brought us the problem doesn’t care whose fault it is—they just need help. “It’s not my fault” lets us off the hook, but it doesn’t do anyone any good. The problem’s still sitting there.
Here’s a different response: “It’s not my fault, but I’ll fix it for you.”
Yes, it’s more work. But you can build a career on it.