"¿Qué le pasa al chico?" signals earlier in the question that your focus is on the boy. If the question were to begin with "qué pasa", the listener would start thinking in a different direction, such as, "What's new?".
Also, "¿Qué le pasa al chico?" flows off the tongue better.
The redundancy is a feature, not a bug, and can be found in many areas of Spanish. As you get used to it you will start to like it.
More information about the redundancy, which I think is also called "reduplication."
I already explained why, if your sentence is ¿Qué pasa al chico?, you need to include a redundant indirect object pronoun.
Now let's look at it the other way around. Suppose the question is
¿Qué le pasa?
Why add "al chico"?
Well, sometimes you don't need to. If the context of the conversation makes clear who you're talking about, then it's not needed (although it can never hurt).
However, if the listener/reader might not know who le refers to, then it's necessary to specify the person you mean.
Spanish has a lot of ambiguity, including with subjects! But we still want people to understand what or whom we're talking about, so it's good to play it safe and add the noun itself. Unlike in English, where you have to choose between using a pronoun or a specific noun (or name), the redundancy sounds very pleasant to the Spanish speaker's ear.