Do we need to rehash the reasons why? You might not have any sympathy for the suckers, or you might not care about attacks on corporate reputations and customers. You might not have any children for the spammers to target, but in that case I think I should extend my sympathies. You don't care about false positives that lose your actual email and you think your time spent with false negatives is too small to matter (and don't care about the multiplication of that time by the millions). You're still getting victimized by the general inefficiency the spammers impose on everyone. Or perhaps worst of all, the basic spammers create noise that helps mask the serious threats of the serious scammers, such as spear-phishermen and identity thieves.
It seems like all of the big email providers have adopted the motto of "Live and Let Spam." Obviously didn't work for Yahoo, did it? Whatever Microsoft paid for the Hotmail brand must have been written off for similar reasons. The google is the saddest case of all, but perhaps that was just the generalized result of dropping "Don't be evil" in favor of "All your attention are belong to us." Anyway, at this point I monitor all three and Gmail clearly has the worst filters, both for false positives and false negatives and for feebleness of their countermeasures. Proof? In the preferences of the spammers themselves, blessing Gmail with the most spam of all.
Doesn't have to be that way. The rational spammers do have economic models that could be attacked. Dropboxes can be nuked and external email services that provide the dropboxes can be pressured. Link shorteners can be subverted against the spammers. Lots of other countermeasures are possible, but the google don't care (and Yahoo can't afford to care and who cares about Outlook).
*sigh* Just venting again, but I really wish someone provided a really good email system, one with tools that would let me help fight the spammers. Why not convert some of the universal hatred of spammers into positive sentiments towards an email system that scares the spammers?