Many years ago, right after digital entered the pro market, I shot a wedding on a digital camera for the first time. Back then, memory cards were wildly expensive so the natural inclination was to shoot JPEG format on all event photos, as those cards filled up quickly.
But what happened that day taught me a lesson I won't forget. The light meter in my trusty Nikon had broken and was severely underexposing every single shot - by about 2 1/3 stops. Now, if you are familiar with photography, you know that is bad news bears. You can't put in data that was never captured.
I had a second shooter that day, so we had photos of the event, but certainly didn't have what the client had expected. It was the first, and hopefully the last time a catastrophic equipment failure ruined someone's wedding photos that I was hired to shoot.
If I had shot RAW format, the client would never have known. Recovering 2 stops in a RAW file is a no-brainer that would be undetectable to a client. At 2 1/3, there might have been a tiny amount of added noise, but still barely detectable.
Since that day, every shot I take is in RAW format, and it has saved me numerous times, both with equipment issues and difficult lighting situations.