STEEM is not only a social media platform, but also content creation platform, and investment vehicle or passive income for investors. It is many things- therefore we should consider saying: users reward (upvote) the contributions to the (STEEM) blockchain.
The popular 90/10 principle was initially popularized by Stephen Covey, the author of "The 7 Habits of Highly Effective People". It assumess that: 10% of life is made up of what happens to you, and 90% of life is decided by how you react.
We can extend this principle to Steemit contents too.
In Steemit, 10% are real useful contents and 90% are junks. However, STEEM inspires content creation. Therefore, creators of all kinds: vlogger, blogger, photographers, musicians, painters, poets are inspired (i.e. economic gain) to create content. However, 90% of these work will be junk like many other fields and 10% will have some worth ( for reading or watching). Out of millions of these blogs, photos, arts etc. some are useful for public through search engine then Steemit is a useful platform. Therefore, don't judge by Steemit's junk contents, there are golds. Similarly, Youtube are full of junk cat or dog videos, but there are lots of useful stuffs too.
However, due to cryptocurrency nature of STEEM, it will attract investors. Those investors may not curator or appreciator of the contents. Some of them are simply investor who mostly care for ROIs. Due to STEEM's delegation feature they may just delegate to 
For some delegation for passive income may be troubling since these investors are doing nothing but profiting. It is not so simple.
STEEM's price is very speculative and fluctuating. Therefore, even if they may make more STEEM, but STEEM's price can go down. For example, if an investor bought 10K STEEM at $60K, even if he earned 2K in 4 months at $3.5 STEEM price he is in loss of $18K ($60K-$3.5x12K). Investor's main skill here is the taking big risk. If STEEM reaches $20, he will make lots of money that seems easy.
But then, why not many investors are doing the same. It is not so easy and simple, it requires gut and experience. Moreover, their buying pressure gives value to STEEM. Therefore, content creators should not judge investors for earning passive STEEM through delegation. Even any content creator can do the same or even upvote their content with their SP.
Another issue is bot vote. It is very competitive, is not guaranteed wining game due to same fluctuation of STEEM or SBD's price. People using the bots are not earning more all the time. Look at the bots ROI in https://steembottracker.com/, they are not profitable these days. It is supposedly used for promotion. Bots are here because anybody can create a bot on "delegation algorithm". No one can ban all the bots. It is necessary evil of the platform for the post promotion not for ROI.
Due to monetary nature of the platform, Steemit or Dtube may see more junks than usual but also it inspire more creation. The inner rules of the blockchain are evolving (e.g. hardforks) to accommodate more creation, reduce junks, attracting investos. Therefore, STEEM blockchain is not only social media platform, but also a mini-economy.
Disclaimer: This opinion is not a financial advice, it is my personal perspective and opinion. Please seek professionals for financial decisions.
Image sources: Most images are open sourced (e.g. Pixabay, Wikimedia etc.) with Creative common license. Some images are used with due courtesy to respected owners.
Thanks for reading.
Cryptominer since 2013, occasional trader and tech blogger
