I've had friends that have gotten into trouble as well. It is very easy to fall into the habit to copy articles and paste the information (plagiarism). There are plenty of other ways to scam the system. I remember that there was one guy that would go around and follow Steemcleaners and comment 10 times a day. Then after a few days, they would self vote their own comment 100% to try to scam the system. I do believe the reward pool would be depleted by hundreds of thousands of micro accounts and individuals if there was no police. Then there would be almost no rewards for those that actually create authentic content. The Steemcleaners system requires servers and people to manage which costs plenty of money to operate and maintain. It is not just good content that is rewarded, but it can also be services such as Steemcleaners.

To answer your question, If there were no downvoting at all, then scamming the sytem will be so high that no one will be able to earn, because there would be millions of bot accounts sucking the reward pool dry. Not only will top earners be greatly impacted, but small accounts will not be able to make any earnings at all. Not only will the top earners be crushed, but no one will ever use STEEM.

If you reduce the payout to something of no value, then you have a social media platform like Facebook, Twitter, Instagram, etc. This is where none of the low popular accounts will earn anything. There would be one difference, unlike those other social media platforms, the highly popular accounts would not make any money either. Thus there would be no incentive to make any good content and develop a following or for that matter to use STEEM social media platform.