Hard to word this right so I'm going to rattle off a bunch of sub-questions to give an idea of what I mean. I'm not interested in the common reasons for a duel (protecting honour etc), more in how the format became popular when it seems like a death sentence for both parties. I'm guessing a lot of this will come down to misconceptions about the format.
How often did both parties get shot? How was cheating policed? (in my head, it seems tough to stop participants turning earlier than allowed, like a false start in racing, and if a fatal shot is fired, there's no second go). Did duelists see it as a skillful pursuit, and is there evidence to suggest that top duelists existed, rather than owners of hair-trigger guns that got lucky a few times?
Finally, the inspiration for the thought, was Alexander Hamilton a total fool to think that firing in the sky could be spotted and reacted to before Burr fired? I read on Wikipedia that duelists sometimes fired at the ground to show courage, was that a common end result and could it possibly happen without a gentlemen's agreement beforehand?
In the UK, by the mid-1700s, there was strong movement in favor of the Pistol over the Sword (not as strong a case on the Continent, where France and Italy continued with the sword), and in large part this was due to the quest for equality. While the sword as the weapon of choice heavily favored the more skillful of the two duelists, the use of firearms, and the rules/conventions which surrounded it, were intended to place the two on as equal a footing as possible. Dueling pistols would come in pairs, as identical as possible, to ensure the weapons were the same. Position and whose Second would get to give the command to fire would be drawn by lots. The window to fire was generally kept very short, to ensure that firing was quick and without much time to aim. Even when rifled barrels in pistols became more available, smoothbores were prefered to keep accuracy from being too high. As such, in the UK, from the turn of the century until its decline in the 1840s, the death rate hovered around 14 percent with fluctuations but overall consistent (Unfortunately, Simpson's statistics don't break down by individual duel, so I can't say what cases saw both killed or injured).
As for cheating, well, as dueling was between men of honor, there was the expectation that you would behave honorably! But there were provisions in place to protect you if your opponent turned out to be quite the cad. The Seconds themselves would be armed, and in theory, fully within their rights to immediately shoot down their Principal's opponent if they acted contrary to the code. I can't recall off the top of my head any incident where this was enforced lethally, but I know of several incidents where the threat was made, most notably in the case of Andrew Jackson when he dueled Dickinson. The latter fired first, and then tried to back away from his mark until Jackson's Second told him, at gunpoint, to return to it. Additionally though, there is the underlying fact that dueling was highly illegal, but courts were willing to turn a blind eye if conducted properly. Duelists charged with murder routinely would admit to their crimes in court, and instead defend themselves as men of honor who conducted themselves properly on the field, something juries would generally accept and find not guilty. The few times you see serious sentences handed out are in cases where conduct was so dishonorable that the jury couldn't ignore the fact.
Despite all this though, you certainly do find a) duelists who nevertheless were accomplished marksmen and not constrained by what limits existed and b) men who gained a reputation for their willingness to duel, often on the slightest pretext, to the point of using it to essentially bully those who didn't let them have their way. In many cases, they would continue to get away with it, although occasionally people would get so fed up that they would turn on the cad and force an end to the matter.
Now, as for the idea of 'deloping', that is, purposefully shooting wide, this was very frowned upon by most 'proper duelists' and essentially all dueling codes. They would call it things such as "childs' play", seeing it as a mockery of the institution. If you were unwilling to actually shoot, the thinking goes, then you should have apologized and not come to the field in the first place. But it didn't stop people. The societal pressure to duel was often just too great for men to feel they could apologize without allowing the other to shoot at them - more than a few recall that they felt a coward because they dueled and true bravery would have been to refuse despite what society expected of them. Perhaps the most famous example of this is the duel by Lord Wellington, then Prime Minister, who challenged the Earl of Winchilsea in 1829. The Earl accepted, and deloped his fire, after which he immediately provided the Duke with an apology he had already written, that he "did not hesitate to declare of his own accord, that he regretted having unadvisedly published an opinion which had given o ence to the Duke of Wellington". Winchilsea had simply felt that he couldn't tender the apology, despite knowing he was in the wrong, without going through the motions of the duel lest he lose face and standing as a gentleman (for his part, the Duke claimed he had only aimed at the Earl's legs, but in any case he missed).