Maybe someone who is completely up to speed can elucidate

[MHMG]

And there's far more to soft proofing than just seeing all the saturated colors that can be output! Anyone that tells you that soft proofing is 100%, is confused or lying. But a 95% match is better than a 80% match and soft proofing is about using the tools we have to better predict the final output. So this idea that soft proofing isn't effective because you're stuck with an sRGB-like display is throwing out the baby with the bath water.

I agree with digital dog...Even if soft proofing on an sRGB monitor is a bit crippled in terms of displaying very vivid colors (as are wide gamut monitors in some instances), it will tell you what additional edits are useful to retrieve losses in global and local area visual contrast (i.e, use a gentle tone curve to bring back some of the lost contrast), and it will  also guide you in terms of what hue shifts have occurred as the out-to-gamut colors get remapped into gamut, so you've got a shot at correcting those issues as well without flying totally blind.When implemented correctly softproofing is your friend

[Lundberg02]

The drum scanner guys used to do grey scale color adjustments all the time. I went over to a shop and watched them do it a long time ago.

[pfigen]

This is veering way off topic, but you mentioned drum scanner guys and I'm not really sure what you're referencing, but as late as the mid nineties, Heinz Webber in W. L.A. was still using a Hell 3010, a great drum scanner that had no visual preview on the monitor. You actually had to use a scope with crosshairs to target a specific area and punch in a CMYK value for highlight, shadow and gray. There were other adjustments available including selective color, but it was pretty much set up to spit out a SWOP CMYK ready for magazine ads. My, how far we've come, even in drum scanning software.