The quality of answers varies greatly depending on "how you ask," even with the same model and same question. "Write something" and "Explain photosynthesis in a way a 4th grader can understand, in exactly 5 sentences, using friendly language" produce completely different results. This "skill of asking the model well" is called prompt engineering.
With generative AI, you can get a substantial portion of desired results without retraining the model—just by writing good prompts. Compared to training and fine-tuning, which are expensive and slow, prompts can be changed instantly and for free