I recently read the elder's manual, from the rexamine.org website.
There is an interesting article on how elder's train ministerial servants to "greet" people at the doors. They are told to be friendly to the those in attendance and to arrive early and stay late to associate with the friends.
In other words, it would seem that the friendliness shown by elders and servants at the halls is more of a duty than a desire to get to know the brothers and sisters.
Many times, elders and servants have been enthusiastic to me in their greetings only, but rarely stop to engage in conversation.
They are not interested in people, only an outward appearance of friendliness, which bolsters the image of the org as having genuine love.