Here's why:
* "por que" is incorrect. The correct way to ask "why" is "por qué" with an accent mark.
* "tu" should be "tú" with an accent mark for proper grammar.
* "hablo" is the wrong verb form. The correct verb form is "hablas" (you speak) since it's referring to the person you're addressing.
A corrected and meaningful sentence in Spanish would be:
* ¿Por qué tú no hablas español?
This translates to: "Why don't you speak Spanish?"
Let me know if you have any other Spanish phrases you'd like help with!