It is basically to prevent misuse of the site, the voting power, the vested power, stopping reward pool rape and selfish interest voting groups. An instance where whales even sought money for voting was found and the person involved had to admit of wrongdoing. In the above case, the whale had voted just before the last 12 hour period began and for a single user who had been paying a percentage. Such misuse is detrimental to the basic goals of steemit