Think about it. Most clerics are attached to a church or cosmopolitan temple somewhere. But somehow, they manage to rise in the church hierarchy, with corresponding divine powers as per the referee. It's hard to imagine the Bishop being 1st level and equally difficult to accept that every one was an adventurer before settling down to lead their flock.
The same could be said for fighters, most of whom serve in a garrison. Magicians are primarily concerned with their books, which doesn't require adventuring of any kind. In fact, magic is one profession that specifically requires sitting for hours pouring over strange volumes, making adventuring a hindrance.
Finally, why would any self-respecting thief risk life and limb against terrifying enemies when they can rob fat, and substantially less dangerous, merchants in the safety of their home town?
So aside from establishing that most adventurers are certifiably nuts, this begs the question: How do non-adventuring types increase in level without risking it all doing so?
|This is REAL cleric training...|
First, it's probably helpful to know what experiences constitute true practice in the first place. The following is a guide, keeping in mind that adventurers get this as well, but faster:
CLERICS study the scriptures and build their faith.
FIGHTERS practice by sparring with each other or against dummies, noting that exercise also plays a part.
MAGICIANS read (and study) arcane books and scrolls, casting spells and sometimes just exposing themselves to magic.
THIEVES case joints, follow marks, and steal from others.
Obviously, adventurers practice all of the above in life-or-death circumstances, so advancement is accelerated. But for those remaining at home, level progression still happens, only slower, being subject to the following:
1) Daily practice nets 1d6 EXP per month (P&P) or 1d6 x 10 using more traditional systems, provided the individual is actively engaged most days as per the referee. This works out to 12-72 per year in Pits & Perils, 120-720 in other systems.
2) Any money earned from professional activities likewise counts towards experience earned, as per the referee's game.
3) Finally, enemies slain also count, provided these are killed through professional means. For example, guards and the like protecting their town from invaders. Sometimes, the local magician helps out, and, of course, thieves often botch things and have to kill (who hasn't learned from their mistakes)...
Of course, lulls in activity, periods of extended peace, and the ever-increasing EXP requirements ensure that most should never surpass 3-5th level, although some will have had prior adventuring experience, and the sky's the limit here.
Clearly, adventurers get it faster. When you regularly have to fight for your life and cast your full range of spells in the pursuit of survival, you get lots of practice. You also get lots of chances to screw up and learn. Obviously, money flows as well, making adventuring an attractive choice for some...
The above explains how the legendary captain of the guard became such a good fighter and earned promotion without ever actually leaving home. But it also helps the referee assign levels to their non-players characters and, possibly, having recurring characters advance over time. Time and skill marches on, after all...