Exactly. I used to be tempted to deduct XP for needless killing, and occasionally did.
I remember old games which gave XP amounts for killing, for example, sheep. It was a minimal amount, but a player thought he was going to be clever and he spent all his accumulated wealth to buy a large herd of sheep, then slaughtered them, expecting an XP boost. He was very unhappy when that didn't happen and all he had to show for his efforts was a field of bloody wool.
That event, I think, is was really soured me to any kind of RAW XP progression.
If you go by RAW and provide level-appropriate combat encounters on a regular basis (even once a week in game time) it's possible to have epic level characters within a few years' of in-game time.
Does it really make sense that a level 1 wizard would roam the countryside for a year and come back with the power to annihilate an entire city with a wiggle of his finger? To me, that is pretty ridiculous.
To get around it, you're forced to provide lots of low-level encounters that provide minimal (if any) XP and space out significant encounters time-wise. Or you can toss out the XP RAW, which is my preference. I dole out levels when it seems appropriate.
The GM that I typically play under cuts XP rewards down to 1/10 of their normal value. I asked him about it, and he says that he still pretty much gives levels when he thinks it is appropriate, too. He just uses the XP because some of the other guys like the sense of progression. It's really a ruse just to keep them from complaining, but they don't have to know that.
As a player, I'm probably in the extreme minority, but XP and levels just aren't a big deal to me. I'd rather enjoy playing my character and trust my GM to provide encounters appropriate to my party's capabilities. Going 20 sessions without any mechanical advancement is fine with me if the game is fun.