The "All the other" Experience happens later. They aren't filed under encounter experience.
But lets just say that I have yet to see a "Diplomat" who ONLY "Diplomats" who hasn't received any combat or magical training... ever get to level 10 in dungeons and dragons.
So I think my experience is safely in the experience category.
But sure, say "Hey, we will give you 10,000 gold so you won't eat me" totally is justification for level 1s to earn 5 levels
I mean it is a life lesson isn't it?
Though it does mean the strongest creatures in dungeons and dragons are diplomats, accountants, and lawyers.
Besides rewarding PCs equivalent Exp for "avoiding encounters altogether" actually gimps them in the long wrong anyhow. So the whole "But then your punishing the PCs" aspect doesn't fly.
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If the players are only killing everyone to try to scrape up exp... Obviously they haven't heard that actions have consequences... or aren't roleplaying.
Meaning you either have bad players or a bad DM
As others (including you
) have indicated, we don't live in the best of all possible worlds where all tabletop players are consummate actors and all DMs are bards straight out of a feudal court. DMs often get lazy and throw out combat encounters one after the other, because it's simple, straightfoward, and doesn't bore the rollplayers. A lot of players, even ones who enjoy heavy RP, will often approach encounters with a very video-gamey/wargamey attitude where pretty much anything that isn't obviously a conversational partner is a threat to be eliminated. Sometimes you'll even have attempts to weave in RP rolled over by the process of combat -- pause for example.
I was playing a monk in a 3.5 campaign. My basic premise was that the character had been found lost in a foreign forest by an aging, hermetic monk. She'd been impetuous and temperamental throughout her childhood, and her master had died before her training was truly complete, so she set off into the world with the ideals firmly fixed in her head, but not ingrained in her behavior. Lawful Good, you say, with a character who tends to go over the line when things turn violent and is too hasty to resort to violence in the first place? Surely you jest, FD! No. I wanted to play the long game with that character, to demonstrate her growth as a person, both moving closer to that old ideal and also growing into her own personality.
The very first combat, guess what happens? It's bloody and nasty. My character downed the main enemy early, but his minions nearly killed the rest of the party. After a long period of me flubbing my rolls while everyone else either lay unconscious and burning or ran away to heal, we eventually won. I announced that I was going to curb-stomp the downed leader on the raised rim around the altar, with the intent of doing one of the two things: if the roll missed, my character pulled the blow at the last second and pulled back her anger; if it connected, I'd play out mounting regrets and guilt over the few days or weeks in-story, and the next combat would play the character as much more hesitant to commit fully, only attacking nonlethally and such.
Instead, guess what happened? First thing said? I don't remember the exact words, but it was something like, "You're Lawful Good, your character can't do that." I don't have anything against whoever it was that said it, but it helps illustrate the issue.
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Back to the main: It's multifaceted. When you deny experience for everything that isn't killing things, players are going to feel pressed to kill more things, even when they ordinarily wouldn't. You don't have to be a powergamer to enjoy the sense of progression and growth -- if you really want to run your political Bioware conversation simulator, I'd suggest not using a system that heavily focuses on combat (or tell people beforehand). When players have more reason to approach things with a kill 'em all attitude, DMs tend to figure that that's what players want, things to kill. RP ends up being discouraged in combat situations because it slows down an already time-consuming process for little apparent reason -- the DM probably didn't design that encounter so that you could talk through it, and you won't gain anything if you do. This whole mentality of rollplay and roleplay as separate and opposing entities has become ingrained in the collective mindset of TTRPGers, and it's thoroughly detrimental.
IMO we should be seeking to do the exact
opposite of tearing roleplay and rollplay apart, we should be working to integrate them more fully, to give rewards to players for being good conversationalists, for arranging clever political maneuvers, for fooling people into giving the party what they want, &c., rather than saying "You only get experience and loot if you kill things, and if you try to kill things you're a bad roleplayer." It splits the base, makes it more difficult for parties to agree on things, and leads to frustration when the DM and players aren't on the same wavelength. I'm sorry if I'm reading you wrong, but what this really comes off as to me is "I don't like players not RPing [and I don't recognize that different people enjoy different levels of RP], so I'm going to make it even more of a pain in the ass to RP!"
Sure, the guy who'll go LG Paladin with an asshole DM and play the role to the hilt even though he's missing out on all the rewards and undergoes constant arbitrary attempts to make him fall, that player will enjoy RPing regardless. The guy that made the face Bard and realizes that charming through situations means no exp and no loot? The girl that made the Barbarian who disarms traps by running through them yelling curses when you tell her that you don't get exp because you didn't use Disable Device? The amorphous blob that made the sneaky poisoner who discovers that they don't get any exp for killing a dungeon full of enemies by poisoning their water supply? They're going to be annoyed, and next campaign they're probably going to play a character who's good at killing things.