This is primarily about decentralization. Our main goal is to always have 20 top witnesses that are all different people. That is the foundation of this blockchain and what makes it secured. If one entity was in charge of all 20 slots then they could do whatever they want and change the rules of the "game" at any time. For example, you could go to sleep one night and wake up the next day to find out that TRON inflated the steem token by 10000% if they wanted to. They could also censor anyone on the blockchain.

Solution: DECENTRALIZE - DECENTRALIZE - DECENTRALIZE