There are a lot of reasons why 'scamming' people is not fun, and offensive to a large majority of players - as clearly demonstrated in the posts.
Let me formulate a definition for scamming: cheat, and/or defraud someone. Yes - that includes cheating.
Scamming includes using cheating software, with illegal methods to modify, or change the game's data to intentionally deceive other players out of items. It is possible to modify the item's data, and change it. More specifically, you could place a copper bar into the trade box; have the cheat software disguise it as a vial of sands, then when the item is traded, the player receives a copper bar.
When 'scamming' is performed, it is not the same type of scamming you think it is. It is players performing illegal activities within the game. That is what is illegal, and offensive. Take the example below:
Suppose that we have two players, player A, and player B.
Player A has been playing the game for 5 years; plays in a guild, farms gold, plays the game fairly often during his time.
Player B, a fairly new player, cannot be bothered with the effort of playing the game, more so, would like to cheat, or scam other players.
Player B comes along and wants to sell an item worth 100k gold. Person A has been farming 100k gold to buy this item for 6 months.
Player B claims to sell an item worth 100k. Player A trades player B 100k gold and receives copper ore, instead of the 100k item. Hence, player A was scammed of 100k from player B.
Up to a year of work was wasted, and taken away from player A, by player B, who thought it was fun.
How would you feel if a player cheated you out of 100k gold through using cheat /hacking software?
Would you sit on your chair and say, "okay I have just been scammed out of 100k gold, but it's okay though. It was my fault - not the person who scammed me using hacking software - but my fault for not thinking the trade was unrealistic. "
I highly doubt you would - and if you did, you would be deluded. Instead, you would be straight up to customer support with screen shots, and videos, attempting to reclaim your gold back, or banning the player who scammed you.
Just because it has never happened to you, doesn't mean it should happen. Because one day - it will.
And when it does happen, you will be making another thread with the completely opposite approach.