they have formed friendships and create acquaintances here on the forum which leads to them being looked favorably upon in the posts. Also, hero members are bound to give out the most merit as nearly all of the merit sources are at least hero or above.
This is something the admin never wanted with the merit post. He has mentioned that one should not give merits to a post just because he agrees to it. Also, giving merits to friends is wrong in my opinion. If you are giving them a benefit for being a friend and awarding merit to their posts over that of a new member, it is partiality for the new member. The new members will then feel discouraged to see this and even those capable of contributing valuable posts here will leave. I am sure the admin never wanted to achieve this with the merit system.