Why would an airline do that and what are they trying to prevent by their actions or even inactions?
It's quite obvious. They want their pound of flesh. They are trying to prevent people coming over to the Emirates, getting a free 777 or 330 conversion and then saying thanks, goodbye. Hell, think about it. Get a job, free accommodation, paid a salary, get the conversion and then leave............If it's just you going, it costs nothing.