Why?
99% of users are non-tech oriented.
Those users will not really be aware of the specific problems with the search results, they won't understand the concept of a good vs bad result and they certainly won't bother to tweak/ban/filter their results.
The 1% that do care and are currently being vocal about it will start filtering their results and they will perceive that the problem is solved. They will stop making a fuss.
So now, the complaints have gone away, but 99% of users are still using the broken system, so the good sites that create good original content are still ranking below the scrapers and spam results for 99% of the users.
The problem must be solved for all (or at least the majority) of users.
(And you can't take the 1%s filtering and apply it to all users in some kind of social search because the spammers will just join the 1% and game the system)