Past as Nologue
Ye olde TL;DR - Beginning with a character of humble origins lets you experience a more fulfilling dramatic progression.
Most modern-style RPG games hinge on the conceit that the player characters, though early in their careers, are professionals in the adventuring vocation. Mechanics like skills, feats, and the like begin at a level of basic, but sure, competence. To match their character’s presumed hardiness, players are encouraged to craft a character backstory that foretells, even foreordains, future greatness.
This premise casts shadows onto the game world’s makeup, too. Professional heroes are prepared, and preparation confers a competence that makes obstacles burdensome, but not challenging. In actual practice, nothing the player characters confront ever poses a dire risk. They will prevail--it is just a matter of how much exertion and time victory costs them.
Heroes aren’t born, they’re made
In OSR games, player characters don’t know what they’re doing and aren’t prepared at first. Simply put, they start with nothing.
All the more impressive, then, when they climb to astounding heights.
Actually, these humble origins make for both rewarding play and compelling narrative structures. Players will derive far more satisfaction from overcoming a challenge their character wasn’t equipped for than one they anticipated. Such a feat requires, and demonstrates, the player’s ingenuity in devising a solution where one was neither apparent nor likely.
Characters with modest beginnings also trace a more captivating--indeed, heroic--development arc than those bearing lofty expectations. When a character completes their journey, the player can rightly revel in the satisfaction of knowing their character took every step themselves.
The character assumes legend, in and out of game, because their achievements weren’t prefigured. Original Dungeons & Dragons (1974) even has a mechanism for this: When your character reaches a high-enough level, they build a stronghold and become woven into the fabric of the game world. This is the sort of narrative coup that is cheapened by even an inch’s head start.
Running starts need room
Taken together, holding your character back at the beginning gives you and the character more room to grow. When you look back and see all the waypoints your character has left in their wake, it will be clear just how much ground they’ve covered.