There are also traditional cuisines of raw beef (such as steak tartar) and many forms of fish (such as sashimi). This still doesn't explain why, but it suggest to me (especially since there are so many types of sashimi) that the real question is why raw pork and chicken (is it all poultry?) are always dangerous, rather than why raw beef and fish are not.

ETA: Gwern has just suggested the same idea.