The reasons why I think YAWYW works are as follows:
First it has flexibility, you can write almost any kind of story you want in it. The only limit (no undoing wishes) has been so challenged and twisted it's almost optional. It can do TG but is not limited to just that. It is also not held to limitations of becoming a specific person, changes being mutual between two people, or pregnancy stopping changing back, unless the author wants his arc to do that.
Second: it is a modern setting, thus familiar and comfortable.
