Why is the organisation so keen? Because it reinforces your 'otherness' from everyone around you.
One of the "I am Mormon" commercials just came on TV. Contrast those ads to the way the Watchtower spreads their message.
Mormons emphasize the ways they are like the rest of us, the ways Mormons are average folks--not their peculiarities, the ways in which they are "no part of this world". Also, the commercials help them make contact with those people who are interested in their message as easily as possible. Using mass media is an effective way to identify potential converts, and to improve their reputation among the population at large.
This ad campaign seems a much better use of resources than printing Watchtower and Awake magazines that go into the trash bin unread, spending longs hours hoping to find one person willing to listen to you, and annoying the neighbors so that they will be unfriendly to you and prejudiced against your religion.
Considering these two different approaches and their results, it is reasonable to conclude that the Watchtower wants the Witnesses to be seen as different, and to emphasize the differences between them and everybody else. That's why it is an effective loyalty test, as I said in an earlier post.