Spam and scams seem able to pursue financial returns through other mechanisms than upvotes, so DV's would seem an ineffective mechanism to censor them. Some spam is not financially motivated. IIRC Bernie almost crashed the platform with spam at one point, and that required changes to code consensus witnesses (temporarily) implemented. Later Resource Credits were implemented, which limited such recursive spamming by the stake held, greatly reducing spam's potential impact on the platform.
You have worked diligently to prevent spam and scams from harming Hive and the community, which I reckon makes you an expert on how this mechanism works. Why do DV's work so well to prevent spam and scams on Hive?