1. Filipinos naturally give answers seemingly inappropriate to the right questions. That's true!
It is called direct answers to one's follow up question/s to the first question.
Q: Kumain ka na?
A: Hindi pa!
Q: Ganun ba?
Q: Kain tayo?
A: Busog pa ako.
2. It's being practical.
It is saving time, saving words. Brevity is the key!
3. Filipinos are fund of short cut.
Why make the conversation long when one can make it short?
4. The best possible answer is not the right answer, but the shortest answer. A dramatic Filipino thinking.