Hmm. I thought you had to have the MSQ complete up to a certain point but according some info I just looked up you just need to be level 50 for Sam and Rdm. That is still a slog to level a job you may not like to get to try another job you may not like. Where as if you could try it out at level 1 and discover you don't like it you could try another job and see if you like that one by making a new character.