I suppose experience does have something to do with it. The wild caught may have had some bad predator encounters.
I also think there is a genetic basis to aggression. All the bull snakes that I caught on the family farm growing up where very mellow and calm within minutes of being picked up. I've caught ones at other locations that never really calmed down.
My first het albino male ball python was a striker. I put it off on coming from a big breeder where he was probably rarely handled (he was about a year old when I got him). However, 2 of his 4 daughters where also strikers until they where about a year old and hissers for another year (both have learned to tolerate me with mild agitation now). Could there be a single gene that can cause aggression? What would one with two copies of that gene be like?
I've heard breeders comment that aggressive animals might make better feeders and perhaps better breeders. Even if that is true I would hate to see the stereotypical calm ball temperament go by the wayside through selective breeding for bad tempers.