Thats because too many unintelligent on the issue people would hear global warming and then use localized data to try and argue against it just like the OP did. Someone looks outside and sees snow and then tries to say global warming is false.
Part of what global warming has done has shift weather patterns. So some places actually have gotten colder, i.e. a shifting weather pattern, but larger areas have gotten warmer.
Also a natural cause of increased warming is more volatile weather due how weather events are fueled by the differences in air temps as as you increase the upper range you increase the fuel.
Thus climate change is a better phrase since its inclusive of all the effects.