Ok, back to your steel, a steel stock sells to the npc's for 80 tria. Now if it was possible to get this item from an npc, by buying it for some little more money, or by doing a quest, don't you think everyone would just do that to get steel and make weapons out of it? Heck, mining iron and coal would be useless at all then. Steel stocks sell between 1000 and 3000 tria each among the players, not if i could get it for 100 tria, why would i pay a player more than ten times as much? No sorry, thats not the way it should be. PlaneShift is a roleplaying game, not like most other mmorpg's which don't deserve the rp in their name. Here it is good that players play their roles and that players interact with each other and player chars are IC'ly citizens as well as NPC's, so why excluding some citizens (player chars) from errands completely?
Besides, Players do give quests too, it happens rarely, but it has happened and I'm sure from time to time it still happens.
Say what you want, but it would already be a quest if a crafter char asks you to get him/her/kra some steel (and in fact, some npc quests do exactly that). Just the reward would probably bigger from the player char, as you learn where the required mines are and also will get some more money for it.
There are a lot of possible quests a Player could give to another Player, the question is just how much is Player A willing to put into making quests and how much are the other players interrested in doing these quests?
If you've done all quests ingame, you probably will know a lot about the settings of the game, about the citizens of yliakum (npc's only), have spent a lot of time interacting with citizens all over yliakum, but still won't know a single player char. Now I ask you, are you playing a multiplayer roleplaying game, or a single player standalone game?

if it was as simple to ask harnquist to give me a quest, then immediately ask the nearest player some rp info and gain item then return it to harnquist it would not be nearly as thoughtful
Whats wrong with that? If the nearest player to harnquist is a smith as well (very likely that will be so), this player will have the needed information for you, if your quest is about crafting. Let me give you an example of what I mean:
(not a real quest tho!)
Player: Hello
Harnquist: Oh, hello. Do you mind, I'm looking for my bronze stock, it must be somewhere around here.
Player: Can I help you?
Harnquist: I have to make this weapon for XYZ and he wants some ornaments made of bronze on it. I seem to have run out of bronze. Could you get me some?
Player: yes
[You got a quest]
Now, you are not a crafter yourself, you have no idea what bronze is made from and where to get the needed metals, so you stand there next to the smith shop:
* Player mumbles something about bronze
Another players is right next to you, the player happens to play a crafter char.
Player2: Excuse me? I've heard you saying something about bronze. I'm a crafter, can I help you somehow?
Player: Oh yes, Harnquist here is in need for some bronze and I have not the slightest idea what that even is.
From here on there are some solutions imaginable, solution 1:
Player2: Ah yes, bronze, a kind of worthless metal made from metal1 and metal2.
Player: Ahh, thank you. Do you happen to know where I could purchase these metals, or even buy bronze stocks?
Player2: I actually happen to have some left over, give me a circle and their are yours.
Solution 2:
I only know where to mine metal1 and metal2. But if you bring me X metal1 and Y metal2 I could make you a stock out of it
and so far and so far, It should just give you and example that player interaction _can_ be useful for quests. It is _not_ a must, but saying it should be completely left out of npc quests is _imho_ the wrong way for a game that combines RPG and MMO to MMORPG

Always keep in mind, that the players around you have probably some information/items/whatever which could be of an advantage for you at one point. Also you can build up IC social contacts that way and won't walk into the tavern after a year of playing to only see people you have not talked to before but have been there all the time too

-- Cebot
PS: a coin always has two sides, doesn't it?
