I don't think politeness leads to finishing last. There are authors here that publish articles that can be controversial. However, I believe that these viewpoints only aim at stimulating a debate not a fight.

In general here on Steemit, it seems like it is better to be positive than negative. This may be because there is an economic incentive here to do so.
A lot people are normally looking for upvotes. If someone left a mean or uncivil comment, the chances of them being upvoted by the original author and others are much lower.

People here are remarkably civil especially when compared other public social media. It's rare to see personal attacks against others which is amazing to see in social media. It remains to be see if something like that would continue if the economic incentive was removed.

Personally, though, I actually enjoy it as I think this politeness actually leads to having more meaningful discussions that involve making more logical arguments than personal attacks.