Partially cause you there's no red mage in this game (yet).
XIV revolves more around the usual MMO trinity than XI did, it being Tank, DPS and Healer. DPS tend to be more solo-friendly for when you're just mucking around the world due to being able to kill things before they kill you. Once you reach 30 on a class (and 15 on a subclass), you can "upgrade" to the class' upgrade that limits the amount of cross-class abilities you can use, but gives you their specialized actions in return.
The starting classes and their weapons are:
Tanks:
Gladiator (Sword and Shield), changes to Paladin
Marauder (Axe), changes to Warrior
DPS:
Pugilist (Fist), changes to Monk
Lancer (Spear), changes to Dragoon
Rogue (Daggers), changes to Ninja, requires level 10 in any other class first
Archer (Bow), changes to Bard
Thaumaturge (Offensive magic nukes), changes to Black Mage
*Arcanist (Damage over Time magic, Pets), changes to Summoner and Scholar (Healer)
Healers:
Conjurer, changes to White Mage
*Scholar, once you get to level 30 arcanist.
*Because they both share the same class, leveling either Summoner or Arcanist levels the other job at the same time.
All in all, arguably the most "versatile" at low levels would be arcanist since they can do more or less bits of all three roles at the start. But really, it doesn't matter because you're gonna wanna focus on what the Job is good at anyway.