It must be emphasised that these settings only affect the on-screen appearance of the image, and not the final result on paper. They can be used to test different printer profiles, rendering intents, etc., in order to view the effect before committing to Print, and then later to apply the same settings while printing from an inkjet printer.
Soft proofing won't be needed if you only display images on the same monitor, and don't print them or post them on the Web.
Using soft proofing, together with proper monitor calibration, AND with accurate printer profiles, is the only way to get a reasonably accurate match between monitor and prin