Soft proofing can be great for those that take the trouble to really understand it - it's just that a lot of people try to skip that bit and see it as a 'tech fix' to save on effort/understanding. I'm also minded to suggest that sometimes it's one of those things that tends to appeal more to those interested in process than content ;-)
As to less 'waste' - well I prefer to see that as part of the ongoing costs of honing my craft - YMMV ;-)