I think alot of people view a head shot on deer as a "risky" shot, lots of stories of bad shots and blown up jaws that cause a deer to run off and starve to death. Deer are typically revered and it bugs a hunter to wound one and not find it, if you can confidently make a head shot do it, it's your call. Pigs on the other hand, well they are pigs. Nuisance animals that don't get much respect. JMHO