It is true that spoken Japanese often leaves much up to context. If you were to translate English sentences into literally equivalent Japanese phrases, you would invariably create phrases with far more syllables. However the language is not used the same way as English. A child will say in English "Mom was angry with me." In Japanese he says "okocchatta." Same information conveyed but requiring context for the Japanese (doesn't explicitly say "mom).

Furthermore, I would argue that when you compare equivalent sentences in English and Japanese, the Japanese sentence often conveys MORE information. Take the English sentence "You did not eat." 4 syllables. There are many ways to say this in Japanese.

A formal translation would be "Anata wa tabemasen deshita." Somewhere between 9 and 12 syllables depending on pronunciation. This sentence conveys a lot of information that the English does not. For example, the use of "anata" instead of a more rough word for "you" suggests that the speaker has a certain type of relationship with the subject. The same is true of "tabemasen deshita", which could have been "kutta" meaning "did not eat", but much less polite.

In myriad ways the Japanese language allows for speakers to be explicit about their relationships with others and their sense of place. English by contrast requires listeners to be more attentive to tone of voice, body language, and word connotations.