In Dungeons & Dragons, if you encounter a trap, you are awarded the XP for disabling it or for triggering it or for accepting the outcome. The only time you don't get the XP is if you somehow avoid it without ever noticing it. It makes sense.
A warrior learns how to shug off the effects of a trap. XP = more hit points.
A thief learns how to disable the trap. XP = higher skill levels.
A lucky person never learns anything because nothing is ever difficult for them.
In Deus Ex and No One Lives Forever 2, experience is never given for killing (except for bosses, but that's because they're mission objectives). It's only given for mission progression, mission completion and finding secret areas.
I like the idea of gaining 75% experience for sneaking. For a lot of the game, there is no need to slaughter every last living thing. In the Orc Camps and the Dark Forest, you could progress quite easily if you just did your mission and killed any opposition you met. There's no need to seek out opposition, but doing so can povide that extra 25% experience.
