Someone answers: The purpose of fitting data to a curve is so that you
can give an exact statement about what will happen in a future
situation like it for which you do not have the data
Is this answer valid? If not, explain and what would you add?
As an instructor, I would probably give half credit for this answer. Here's why: Yes, a primary purpose of the regressed model is to make future predictions. I wouldn't add anything to that -- if anything, the quoted response is already unnecessarily wordy to the point that it seems suspect. (Nonetheless, I'd be charitable and give half credit for that part.)
The real problem is the phrase "give an exact statement about what will happen in a future". That's incorrect and simply impossible. Any predictions we make are necessarily estimates (possibly expressed with a likely range of error). It should be obvious that no one is able to make "exact" predictions about the future, whether one thinks of examples like weather forecasts, financial markets, sporting events, etc.