Why? Don't you have any strong arguments yourself? You started this thread, yet don't have any rational argument in their favour.
We know that they exist, and we know that it's possible that spammy Joe's blogspot (click the ads and support the sponsors) may convert better for advertisers etc. So what?
They simply don't help visitors find information they need better than Google/MSN/Yahoo etc., which seems to be the only argument you have for them.
I'm not anti scrapers totally - I just find them annoying, as unlike your portrayal of them, they mostly don't have relevant scraped links - just garbage and ads. How does that help visitors searching for specific information? It's true that some are better than others, but it's a rare site that is any good.
They are a reality, and we live with them. There is one scraper site I'm especially grateful to in my niche - I liked his format so I "borrowed it". Unlike his site, my page that apes his contains *actual information*. I suspect due to my position in the serps I'm doing rather better with his format - tee hee.