grammar - Why does English need an article before any noun?

In my native language, we can say:

I have dog

Because I don't want to say a dog (one dog, how many dogs) or the dog (that dog, the listener don't care which dog).

p.s. after 3 years later, I have to say, why I ask this question, is I still cannot grasp how to use the right 'article word'. sometimes, a noun will use an article, sometimes, a noun could not(or omit) the article word before it. there aren't a formula for this. So, I have to remember all the time! I feel so frustrate

Answer

Well, first of all, we don't need an article before any noun. I can say:

I like dogs.

As to your question of why, the answer is, "because that is how English works".

The articles perform a discourse function, by indicating new and old information. They often evolve from demonstratives (e.g. "this" and "that"). They evolve independently in unrelated languages. Normally, once an article system becomes a part of a language, it is an all-or-nothing thing. This is not unlike a verbal inflection system, a gender system, or a case system; once the system is in place, it is not optional.

Aside from this, there isn't really a more concrete reason for "why" English works this way.