In some cases people might not be seriously considering getting a paid account since they feel like it's a wasted expense, but since it's a free thing to try, they check it out anyway. Once that runs out, maybe the $3 purchase goes on the consideration list after all, because they've seen what it is and can decide better if it's worth it.

I understand the "wow, it's just $3 and you get a month to play!" but if people want to weigh it before deciding if those $3 should go here or some other service, it seems like it's fair to allow that.