I think it is a combination of two reasons:
1.) It has to be readable for Westerners, so you have to pick something for Chinese that Westerners can read;
2.) You want to be consistent in picking an abbreviation: you don't want to use one method for one language but another method for another language, because controversy about ethnic issues arises easily.
Country codes are both readable and "objective" in that at least they already exist officially. Language codes à la Wikipedia exist, but they are perhaps less visible and well known, compared to country codes, which are on number plates. As to which country to pick for which language, I think they usually pick whichever country is most closely associated with the language in question. Even though more people in Mexico etc. speak Spanish than people in Spain, it is still Spain that is seen as the historical "locus" of the Spanish language. Another concern is whichever country the item is most likely to be sold in.
I'm sure Hebrew would be whatever the country code for Israel is. Arabic is a good question: it may be the country code for Saudi Arabia? It's also in the name of the language. The same applies to England and English. Perhaps it is a rather arbitrary choice of method, but you know what people are like.
Note also that it is not always consistent: I have seen different codes for the same language. I have even seen B for Dutch on occasion, for something that was probably intended for the French market but was also occasionally sold in Belgium. I've also seen EN for English. Perhaps you will sometimes see AU when you're in Papua New Guinea or something.