#BeginOfRant
Why there are so many "do" and "don't" about Italian food? Same reason why there are so many weird rules about how to dress, how to behave on a LoL server etc: soft power.
If you have a ton of pointless rules you can create a in-group and a out-group. And since people want to be in the in-group, you now have some degree of power over them.

This is neither new, nor limited to Italian food, but in any case you better remember that 99% of those rules make no sense.
#EndOfRant