Today using the wrong fork to eat a salad at a dinner party would not usually qualify as deviance. why not?

Because It is not a serious enough norm violation to provoke sanctions.

Of course, in some society, there is a norm that regulate the correct way or posture to eat properly.

But the violation of things such as fork using usually just being overlooked because it does not give any impact to both the individual who did it and the people around them.