Soft proofing in Photoshop seemed like snake oil until a banner came back neon green
I used to skip soft proofing because my monitor is calibrated so why bother, but after a 6 foot banner for a shop in Denver printed with greens that screamed like a traffic light, I ran a side by side test with 10 files and now I won't export a single CMYK job without checking it, so which camp are you in, trust the numbers or trust what you see on screen?