The problem with jobs is they aren't meant to be leveled. If you look at the list that was given you would notice that all jobs only have 5 abilities. This ties into the concept that we are given 15 class abilities, 10 free slots and then 5 slots left open which take the role of what the job abilities are. Jobs aren't their own self-defined class they are a class enhancer and as such level up along with your class rather then act as it's own. If they planned out jobs to have more abilities and traits of their own I could understand wanting the 1-50 experience however based on what is known, the experience of jobs will be told through quest. So even a person who is a 50 Pugilist won't have access to all the Monk abilities once they unlock the Monk job, they'll have to do all the quest before obtaining them all which could mean that each job has 5 unique quest attached to them starting at 30 and going from 35/40/45/50.

It's also unclear as to how challenging the quest may be, they may be simple lore based enjoy the plot quest or omg defeat this annoying mob kind of quest. Heck if you consider the current meta-game of xp the sense of accomplishment is basically hindered on the current method of being able to PL, so pretty much if you gave levels to those jobs it wouldn't be people grouping together fighting leveling it up the fastest, but the linkshell with the most people PLing their friends to the cap level.

Overall Jobs are there own entity, used to give the class a defined role, it's as simple as that, to complex it anymore would add an unnecessary time sink if the only outcome at 50 was having access to 5 abilities. In the future there could be different concepts to the job system or even needing certain jobs unlocked to unlock new classes. But ya that's all in the future and even the jobs themselves aren't til 1.21 so things can change but I doubt they will change to become their own identity.