First off, putting on my admin hat, if this thread acquires the acrimony most threads about Job vs. Class RP have, I'm gonna lock it ASAP. All, please don't make me do that. 
Taking off my admin hat and speaking personally, I think a lot comes down to the mixed messages of the game. First, you can be those things in game; you can be a White Mage and use Regen, Holy, and the like in game, so why shouldn't you be allowed to RP it? While I don't think this is an especially strong argument (after all, you can wield the legendary Thyrus in game, but one wouldn't advocate RPing it as that specific weapon), it's very strong for some. Its strength is bolstered by the narratives on the official site, where they say things such as...
Regarding Jobs generally: "Jobs refer to those martial paths that thrived in former times but have since fallen into disuse. Recent developments, however, have occasioned something of a revival in their popularity."
Regarding White Mage: "Although the art subsequently became forbidden, it is now in the midst of a revival at the hands of the Padjal, chosen of the elementals."
So, the official site purports that the Jobs are being revived and that the rarest of the rare by its own quest lore (White Mage) is actually in the midst of a revival. When you combine that with the fact that we as RPers generally discard or make generic parts of quest lines that purport the player character as the One True Hero, a person could write a narrative that explains how they have access to the power through a means different than that proposed by the quest line in game and have lore support for it. Many RPers are willing to accept a plausible narrative justification in these circumstances.
Finally, adventuring PCs are a significant minority of the population of Eorzea. So, one might argue that rarity is still enforced even if every PC adventurer uses a Job, because adventurers themselves are a tiny group of people compared to the masses who populate the continent.
Full disclosure: my character is not RPed as having access to any of the Jobs, except for Summoner. So, I'm just summing up the arguments I've seen; I don't personally RP a character that uses them.
Taking off my admin hat and speaking personally, I think a lot comes down to the mixed messages of the game. First, you can be those things in game; you can be a White Mage and use Regen, Holy, and the like in game, so why shouldn't you be allowed to RP it? While I don't think this is an especially strong argument (after all, you can wield the legendary Thyrus in game, but one wouldn't advocate RPing it as that specific weapon), it's very strong for some. Its strength is bolstered by the narratives on the official site, where they say things such as...
Regarding Jobs generally: "Jobs refer to those martial paths that thrived in former times but have since fallen into disuse. Recent developments, however, have occasioned something of a revival in their popularity."
Regarding White Mage: "Although the art subsequently became forbidden, it is now in the midst of a revival at the hands of the Padjal, chosen of the elementals."
So, the official site purports that the Jobs are being revived and that the rarest of the rare by its own quest lore (White Mage) is actually in the midst of a revival. When you combine that with the fact that we as RPers generally discard or make generic parts of quest lines that purport the player character as the One True Hero, a person could write a narrative that explains how they have access to the power through a means different than that proposed by the quest line in game and have lore support for it. Many RPers are willing to accept a plausible narrative justification in these circumstances.
Finally, adventuring PCs are a significant minority of the population of Eorzea. So, one might argue that rarity is still enforced even if every PC adventurer uses a Job, because adventurers themselves are a tiny group of people compared to the masses who populate the continent.
Full disclosure: my character is not RPed as having access to any of the Jobs, except for Summoner. So, I'm just summing up the arguments I've seen; I don't personally RP a character that uses them.
The Freelance Wizard
Quality RP at low, low prices!
((about me | about L'yhta Mahre | L'yhta's desk | about Mysterium, the Ivory Tower: a heavy RP society of mages))
Quality RP at low, low prices!
((about me | about L'yhta Mahre | L'yhta's desk | about Mysterium, the Ivory Tower: a heavy RP society of mages))
