On the point of view that Admins think about what players want:
RO has been here for very long now, maybe too long, even. That said, it's been a long while since anything this extensive has been introduced, maybe since the implementation of transcendent classes. Thus, some players (like myself) want to have a taste of what's coming, to deviate from the usual things you play RO for. It's like... a "custom" that you know will be implemented (eventually) in all official servers, and (later still) in majority of private servers, so you can prepare yourself on what's coming. And even if it's gamebreaking to implement third classes, well... the admins of those servers made their choice and surely they know all about the risks of doing so.