Steemit is very different compared to other websites that allow you to make money. On other websites create content and it will earn you money as long as the topic is relevant. On steemit you earn on the basis of how much steem you own. Life of content is just 7 days. The more steem you stake, the more will be probability of your earning. Since there is an investment involved people feel it is their right to abuse the system by voting their comments 100%.
Also the people who own a lot of steem think that they own this platform and set rules thinking the same. If steem really wants to stay truly decentralised then it has to curb this abuse of power.