Important thing about P&P RPGS, is that you by no mean meant to earn xp only in combat. If you can resolve the situation without engaging in combat (persuasion, threats, or simply by stealth) - you would still earn full 'combat' xp, from enemies you would fight otherwise.
Of course would later decide to attack foes from which you already earned xp - you will gain no additional xp.
As you understand in CRPG based on D&D it's just as important. If social chck would just clear area of enemies, by will not grant you xp (or not enough xp) - ppl would avoid any social checks, so they would be able to gain more overall xp. And that's unfortunately would be quiet sad experience.
