The reward to be earn will always motivate people to be here on steemit. Therefore all kinds of people whether good intention or bad will try to earn more money. Like you said all steemit participants are in a way investors to steemit, stackholders if they have SP, so at the end of the day bottom line if people want steem to last forever the use of the platform should have only good intention.
There are plenty of ways to earn crypto in the space, and steemit is no different. The self upvote on comments is definitely getting worse I think. I kind of feel jealous when I see users who upvote themselves over $1 for a two to five word comment. The fact that SBD is currently more in value than Steem is enticing users to buy delegated SP. Some use those SP to upvote other's content while others do massive upvotes.
Looking from an investor perspective he or she bought the delegated SP in hopes to earn more than what they put in. That in a way is using steemit platform to earn more. It takes time and somewhat luck to be able to figure out ways to earn more on steemit. I think of this as a free market play where people make a bid for items in hopes to sell back later for profit. The self upvotes in turn hope for bigger returns. However in free market there will be a point where the bubble will burst. When it becomes a lost to buy a upvote from a bot or steem delegation to upvote one's content.
With less than 1 million users on a 7+ billion population it seems steemit is in its infancy. When free market does play out we may or may not still have a working steemit. I hope its a working steemit :)