I am not a person who goes on tours, I make my own arrangements and like the experiences that allows, so back in the day when I was still a JW and they were promoting these trips, I always felt that if I wanted to go to a convention in Poland, I would go if I wanted to and would not need any approval from anyone.
The assemblies are open to the public, what would keep me from attending even though not part of the official group? I remember hearing the prices and thoujght they were not a very good deal. Like heathen mentioned, there was a little bit of envy involved with those who couldn't afford the overpriced trip.
This reminds me of the approval they now require to be able to work on a quick build. What a crock.