According to the concept of Steem witness, witnesses are the people who are chosen directly by the community to run the blockchain and its operations. For this purpose every account has been given a right to chose the witnesses. A person can chose maximum 30 persons as witnesses. However, witness voting is not like our tradition voting system in which every vote has equal value. Here value of a vote depends on the amount of vesting one have.
Vesting depends on Steem Power (SP). SP is influence token. The large SP one holds, the large effect its witness vote will have. Hence, thousands of witness votes of minnows and plankton are not worth a single witness vote of a whale. This is the reason that the witnesses don't care about the votes of minnows and plankton. They always sought favor of large SP holders viz. @freedom et al. It seems that most of the top witnesses know each-other well. They may be from a group which adopted Steem in its earlier phase. It is not bad for a group of person to invest in a venture and take advantage from it. It seems that they are also backed by Stinc, otherwise, they could not have made their impression on this platform. They are also the investors on Steem coins. Hence, like every other investors, they also like to get a fair return for themselves. In fact, nothing comes free in this world, including free cryptocurrency.
It seems that top 20 witnesses are under the influence of Stinc as they don't have other means. Till date Stinc and its founders are the largest SP holders. Hence, witnesses cannot defy Stinc as it may have bad consequences for them. During HF20 it was seen that HF20 was implemented hastily even after the opposition of some top witnesses but Stinc was bent on going with the software which was untested. That resulted in complete stand still over a week. It shook people's belief on this platform. Many left the platform and many active users became dormant. It also made difficult for newbie to make a place on this platform. So, it can be said that there is a need of democratic reforms on this platform.
To the extent Steemit Inc does not want things to appear that way, not. But practically everybody knows that the Steem Inflation hasn't made the stake distribution decentralized enough, yet. But we're getting there. I don't think we're in any kind of an acute danger because of it because it seems that everybody's learned a lesson or two from the HF20 hickups.
These 20 accounts belong directly or indirectly to Steem Inc. Jump ship or fork from Steem if Steem Inc starts to do shizz.