I have spent a great deal of time reading ghost stories and studying ghosts, so I don't think it's too much to assume that a lot of hauntings result from traumatic deaths. Yet it's interesting in many hauntings how mundane most ghost sightings are. Even battlefield ghosts tend to be seen and not heard, and generally the sound of fighting is somewhat nondescript. What amazes me though, is how little you hear about angry, cursing ghosts. Angry ghosts are fairly common, but not particularly cursing. If I was fighting for my life, I'd probably be cursing.
Some might argue it's a difference in eras. Most history would have you believe that people were more genital (Ed. note: I originally mis-wrote this as "gentile," when I meant "genteel," so I decided to correct it as "genital" because, hell, what the hey?) in times past, but I don't believe that to always be the case. The American western frontier was occupied by many single men, and wherever there are single men, there is cursing. And there were enough gun fights resulting in fatalities that there should be angry, cursing, ghostly gunmen.
Perhaps the ghosts didn't know they were going to die and weren't prepared to swear. While possible, that couldn't always be the case. A gangster getting gunned down by G-men would most certainly know what was coming. And I don't think he'd have very kind words in that situation.
It'll be interesting to see if future ghosts take on more of the attitude of this era—and I wouldn't see why not considering that if someone dies now, they will always be from this time. That being the case, maybe there will be more swearing ghosts. Just once I'd like to read about a ghost that yells out "motherfudger."