The more steempower someone has, the more his/her vote is worth and by upvoting the blogs/posts he likes he is rewarding the authors a portion of the daily "mining rewards"
It also translates to "The richer you are, the more his/her vote is worth and by upvoting wives/gf/buddy/friends/relatives/new-friends-they-got-to-know-on-steemit/authors-who-usually-got-upvoted-a-lot-even though-their-content-is-shit a portion of the daily "mining rewards" which come from the pockets of investors e.g. Laonie who invested with 400 BTC"
What a "great" idea to get ultra rich within 6 months... I am sure steemit bloggers and the founders can sleep well at night :p