A literal translation is fine, but in English "We hear you" = "We are listening to you" are interchangeable. They have the same meaning. If anything, "We hear you" is more emphatic. The French (i.e. in a restaurant) have a lovely habit of repeating your question/statement in a different way, just to ensure everyone understands each other. This is the same kind of thing.
It's simply a different grammatical construction in French. Conversely, you can ask yourself why we need a preposition with "listen" (to) or "look" (at) in English, where it's not needed with similar sense verbs like "hear", "taste", "smell", "feel", or "see".