While I tend agree, it sounds too obvious to be a solution. I would suggest that because Google can't detect all bad links, they want to make the ones they do

While I tend agree, it sounds too obvious to be a solution. I would suggest that because Google can't detect all bad links, they want to make the ones they do detect "hurt" more. If Google simply zeroed out negative links there would be no repercussions for webmasters building massive amounts of bad links. Sort of like throwing link pasta against the wall. If you build enough crappy links, you will eventually find areas of the web Google has yet to police, therefore you're always slightly ahead. With penalties in place, those bad links might not be worth building because the penalties will outweigh the benefits of building massive amounts of low quality bad links.